investigation into exposure when the visor of air fed … · investigation into exposure when the...

Prepared by the Health and Safety Laboratory for the Health and Safety Executive 2015

Health and Safety Executive

Investigation into exposure when the visor of air fed RPE is raised during spraying

RR1064Research Report

Mike Clayton BSc and Nick Baxter MScHealth and Safety LaboratoryHarpur HillBuxtonDerbyshire SK17 9JN

Air-fed visors (AFV) are commonly used within the Motor Vehicle Repair (MVR) trade for protection against exposure to isocyanate paints. However, a common practice amongst paint sprayers is to flip up the visor of their AFV immediately after spraying to check the quality of the paint finish. This may be only for a few seconds but if repeated numerous times during a work shift, this could potentially result in a significant increase in exposure. The aim of this project was to determine the reduction in protection and thus potential increase in exposure when the visor is lifted and to explore potential engineering solutions (by modifying the AFV design) to prevent exposure during any visor lift.

The results clearly demonstrate that lifting the visor whilst still within a contaminated atmosphere had a significant detrimental effect on the protection afforded by the AFV. Mean protection factors were measured at 1.7 in the lifted position and at 2.7 over the whole of the exposure period (from start of the lift to recovery of protection after refitting). This latter figure equates to a 15 fold increase in exposure when related to the assigned protection factor of40 for AFV when used correctly.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.


HSE Books


© Crown copyright 2015

First published 2015

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Acknowledgements

The authors would like to thank the external stakeholders within the motor vehicle repair trade who invited HSL researchers onto their sites. The authors would also like to thank David Fox, HSL, for conducting the interviews with the sprayers and the HSL volunteers who participated in this project.

ii

iii

KEY MESSAGES

Respiratory protective equipment (RPE) is extensively used to protect workers against

inhalation of chemical hazards. When correctly selected, maintained and used, RPE is capable

of providing effective control. However any deficiencies in the supporting programme that

underpins the management and deployment of RPE, or any poor workplace practices can reduce

the overall protection provided.

A common type of RPE used within the motor vehicle repair (MVR) trade for protection against

exposure to isocyanate paints is a supplied air device commonly referred to as an air-fed visor

(AFV). These devices are easy to don and doff and suit the types of activities undertaken by

paint sprayers. However a common poor workplace practice within the MVR trade is for

sprayers to flip up the visor of their AFV immediately after spraying to obtain a better view

when checking the quality of the paint finish. While the visor lift may be only for a few

seconds, this action, especially if repeated numerous times during a work shift, could potentially

result in a significant increase in exposure. The majority of sprayers interviewed during this

project stated they lifted their visor.

A series of tests have been undertaken to determine whether any degree of residual protection

remains when the visor is lifted and the implications of a visor lift on potential increase in

exposure. The findings of the tests, conducted using both a breathing simulator and test subjects,

show that the degree of residual protection provided by the visor when in the lifted position is in

the approximate range of 1 to 3.7 (mean 1.7) and the protection factor measured over the whole

of the exposure period (from start of the lift to recovery of protection after refitting) is in the

approximate range of 1.4 to 9.0 (mean 2.7). In terms of increase in exposure, this mean value of

2.7 equates to an approximate 15 fold increase in exposure when related to the assigned

protection factor of 40 for an air-fed visor when used correctly. Although only a sample range

of air-fed visors were tested, due to the fairly common design across this type of RPE, the

findings can be applied across all types of air-fed visors. In summary, the results of the tests

clearly demonstrate that lifting the visor whilst still within a contaminated atmosphere

significantly increases the wearer’s exposure.

It was found that when the visor is replaced after being lifted, it takes a period of time until the

protection provided by the RPE recovers to the level prior to the lift. This period of time was on

average about 15 seconds. In the terminology of the MVR industry this period of time could be

likened to the spray booth clearance time and could be referred to as the RPE clearance time.

Therefore it is important to note that increased wearer exposure is not just restricted to the lift

duration.

Additionally, a number of modifications were applied to the most common type of visor to

explore whether there is scope for improvement in design that would mitigate exposure during a

visor lift. Modifications that led to a significant improvement in protection were those that

maintained a clean breathing zone around the wearer’s mouth and nose. One was the addition of

a loose fitting inner mask positioned inside the visor that remained in place when the visor was

lifted. The second was a modification incorporating a window slit which removed the need to

lift the visor to obtain an unobstructed view of the workpiece, thus still maintaining a clean

breathing zone around the wearer’s mouth and nose.

Another common practice amongst sprayers was to apply masking tape over the edge of the

tear-off visors to prevent any over-spray from depositing on the main visor. This action

prevented sprayers from removing their tear-off visors whilst in the spray booth which may

have allowed improved vision and thus removing the need to lift the visor.

iv

EXECUTIVE SUMMARY

Study aim

The aim of the study was to determine the degree of potential exposure to an airborne

contaminant when the visor of an air-fed visor (AFV) is lifted and to explore potential

engineering solutions to reduce exposure during a visor lift.

The study had the following objectives:

Gather information relevant to visor lift by conducting informal interviews with paint

sprayers from the motor vehicle repair (MVR) trade.

Determine the reduction in protection and thus the potential increase in exposure as a

result of a visor lift by conducting a series of tests using a dummy head and a breathing

machine using a range of AFV.


result of a visor lift by conducting a series of tests using volunteer test subjects using

two models of AFV.

Explore engineering solutions to enhance residual protection during a visor lift.

Develop an illustrative tool to demonstrate the effect of visor lift on protection provided

to the wearer.

Develop an exposure model for determining exposure or reduced protection given a

number of input variables including visor lift duration, visor lift frequency and wear

time.

Main findings

The findings of the tests conducted using both a breathing simulator and test subjects, show that

lifting the visor had a significant detrimental effect on the protection afforded by the AFV. The

degree of residual protection provided by the AFV when the visor is in the lifted position is in

the approximate range 1 to 3.7 (mean 1.7). The effect of the visor lift on the protection afforded

needs to also include the time taken to lift the visor away from the face to the lifted position, the

time the visor is in the lifted position, the time taken to refit the visor to the wearer’s face, and

the time taken for the protection to recover to its previous level. The protection factor measured

during this whole exposure period is in the approximate range 1.4 to 9.0 (mean 2.7).

Using the mean value taking the whole exposure period into account, the increase in exposure

during the period of the visor lift is approximately a factor of 15 when related to the assigned

protection factor (APF) of 40 for an AFV when used correctly. In the simulation spraying tests

carried out in this project the AFV typically returned protection factors >10,000 when worn and

used correctly. Relating the effect of the visor lift to a protection factor of 10,000 instead of the

APF of 40, equates to an increase in exposure during the period of the visor lift of

approximately a factor of 3700.

To put this increase into context, it has to be related to the total daily AFV wear time based on a

typical number of spraying sessions per day. The majority of sprayers interviewed stated they

v

lifted the visor at least once during each spraying session, and therefore assuming a lift time of 5

seconds, the potential increase in exposure based on the APF of 40 is a factor of 1.2, and on a

protection factor of 10,000 is a factor of 52.

Although only a sample range of air-fed visors were tested, due to the fairly common design

across this type of RPE, the findings can be applied across all types of air-fed visors. In

summary, the results of the tests clearly demonstrate that lifting the visor whilst still within a

contaminated atmosphere significantly increases the wearer’s exposure.

It was found that on refitting the visor after a lift, the protection to the wearer took

approximately 15 seconds to return to 80% of the level before the visor lift. We have referred to

this as the RPE clearance time. The mean RPE clearance time was found to be approximately

15 seconds for Model A (the most common model used in the MVR trade and in which the air

inlet is built into the chin area of the visor) and 16 seconds for Model F (which has the air flow

inlet in the head-top providing an air flow down across the wearer’s face), and this value did not

vary with lift duration. The RPE clearance time should be added to the lift duration time to give

a total exposure time to the wearer.

A number of modifications were applied to the most common type of visor to explore whether

there is scope for improvement in design that would mitigate exposure during a visor lift.

Modifications that maintained a clean breathing zone around the wearer’s mouth and nose led to

a significant improvement in protection. This was achieved with the addition of a loose fitting

inner-mask positioned inside the visor that remained in place during the lifting of the visor. If

adequate protection can be achieved with a loose fitting mask then the discomfort issues

associated with a tight fitting mask will not occur. Another modification explored was to create

a slit in the visor to enable an unrestricted view while keeping the main body of the visor and air

inlet in place. This window slit configuration also maintained a clean breathing zone around the

wearer’s mouth and nose. Other modifications explored repositioning of the air distribution

system inside the visor, an air curtain blowing across the breathing zone and variation in air

flow rates into the visor.

Another common practice amongst sprayers was to apply masking tape over the edge of the

tear-off visors to prevent any over-spray from depositing on the main visor. This action

prevented sprayers from removing their tear-off visors whilst in the spray booth which may

have allowed improved vision and thus removed the need to lift the visor.

Additional findings from the site visits

Whilst all sites visited had an acceptable level of record keeping in relation to servicing and

testing of the spray booth and breathable air compressors, the record keeping covering the

maintenance of the AFV was generally poor or non-existent. It was common for the AFV to be

personally issued and the sprayers responsible for their maintenance. Although heavily

contaminated with paint the AFV in use at the time of the visits were generally in a reasonable

condition and when used correctly should be capable of providing adequate protection. There

was no structured RPE training for wearers; instead firms relied on the sprayer’s ability to pick

up correct use and/or their prior employment experience.

vi

CONTENTS PAGE

1 INTRODUCTION .................................................................... 1

1.1 Background 1

1.2 Effect of a visor lift 1

1.3 Study aim 2

2 IMPLICATIONS ...................................................................... 4

3 MOTOR VEHICLE REPAIR BODYSHOP SITE VISITS ......... 5

3.1 Objectives of the site visits 5

3.2 Setting up and carrying out the interviews and observations 5

4 AIR-FED VISOR TYPES INVESTIGATED ............................. 6

4.1 Models selected for the study 6

4.2 Designs of air-fed visors 6

4.3 Air flow measurements 10

5 METHODOLOGY ................................................................. 11

5.1 Dummy head non-breathing 11

5.2 Dummy head and breathing machine tests 11

5.3 Simulated spraying tests using human subject tests 12

5.4 Visor improvement 14

6 MOTOR VEHICLE REPAIR BODYSHOP SITE VISITS ....... 19

6.1 General 19

6.2 Summary of main findings 19

6.3 Implications for main study 21

7 TEST RESULTS................................................................... 22

7.1 Terms and definitions 22



7.4 Simulated spraying tests using human subjects 25

7.5 Visor improvement tests 25

8 DISCUSSION AND CONCLUSION ...................................... 28



8.3 Simulated spraying tests using human subjects 29

8.4 Visor improvement tests 29

8.5 Illustrative visor lift video tool 31

9 REFERENCES ..................................................................... 33

APPENDIX A- MOTOR VEHICLE SITES VISIT REPORT ............ 34

vii

APPENDIX B – BREATHING MACHINE DATA ........................... 38

APPENDIX C – SIMULATED SPRAYING TEST DATA ................ 39

1

1 INTRODUCTION

1.1 BACKGROUND

HSE guidance on the control of exposure to isocyanate paint spray (HSE 2014) promotes best

practice for the selection and use of respiratory protective equipment (RPE), recommending that

air-fed half face mask breathing apparatus or air-fed visors (AFV) be used. For reasons of

comfort and wearer acceptability – ease of use, and greater field of view - AFV are the most

common RPE choice. Isocyanates are recognised as a cause of occupational asthma (HSE,

2010). Spray painters using isocyanate-based paints in the motor vehicle repair (MVR) trade are

a group at risk of exposure.

Previous laboratory and workplace studies carried out by HSL (Bolsover, 1996, 2006; Vaughan

and Rajan-Sithamparanadarajah, 2005) concluded that AFVs are capable of providing adequate

levels of protection when correctly used and maintained. Vaughan and Rajan-

Sithamparanadarajah in their application of a data treatment method to the workplace data set on

air-fed visors (Bolsover et al, 2006), concluded that a fifth percentile protection factor value of

312 could be drawn from the data.

Therefore taken at face value, AFV should provide an adequate degree of protection when

correctly used, however poor workplace practices can have a negative effect on the protection

provided. One such negative practice is for sprayers to lift or flip up the visor of their AFV

immediately after spraying to check the quality of the paint finish. This is done because there is

only a short period of time (up to about 20 seconds) while the paint film is ‘wet’ and further

paint can be applied if necessary without compromising the finish (Sanders and Davies, 2006;

Jones et al, 2012). Sprayers lift up the visor to obtain a better view of the paint finish than that

when seen through the visor of their AFV. The short period of time while the paint film is ‘wet’

is not sufficient time for the LEV inside a spray booth to reduce the isocyanate concentration in

the ambient atmosphere to safe levels. While the visor lift may be only for a few seconds, this

action, if repeated numerous times during a work shift, can significantly increase AFV user

exposure.

1.2 EFFECT OF A VISOR LIFT

RPE when selected, worn and maintained correctly is assumed to provide protection at or

greater than their assigned protection factor (APF). Therefore when an AFV is used correctly

within an effective RPE programme, it is assumed that the protection provided to the wearer

over their shift will be at least a protection factor of 40 (BSI 2005a). In terms of exposure, using

RPE with an APF of 40 should result in a wearer’s potential exposure being reduced by at least

a factor of 40. AFV are loose-fitting RPE, i.e. they fit loosely to the wearers face and rely on a

sufficient air flow through the device to maintain protection, therefore, if the visor is lifted

whilst the wearer is still inside a spray booth and before the booth clearance time has elapsed,

the wearer is likely to be exposed to any residual airborne paint spray.

Unless there is any residual protection provided by the AFV when the visor is lifted, the period

of visor lift can be treated as a period of non-wear. The effect of just a small period of non-wear

can greatly reduce the protection afforded. During the non-wear time the protection factor

effectively falls to one (i.e. no protection) and this leads to a significant reduction in the overall

protection provided as can be seen from the graph in Figure 1.

2

Figure 1 Effect of non-wear time on Protection Factor. The solid line represents a starting protection factor of 40. The dashed line represents a starting protection factor

of 312

For example, if the visor is lifted 5 times for 10 seconds for every 15 minutes of wear during

spraying, that is equivalent to a non-wear time of 5.6% (50 / (15*60) * 100). This has the result

of reducing the protection factor from 40 (based on the APF for an AFV complying with the

requirements of BSEN14594:2005 (BSI 2005b) and shown as the solid line in Figure 1) to a

protection factor of 13. This is a significant reduction in protection, which in terms of increased

exposure is equivalent to approximately a three-fold increase in exposure. Since 95% of wearers

should be achieving protection factors >40, if we apply the non-wear time calculation to a PF in

use of 312 (Vaughan and Rajan-Sithamparanadarajah 2005; shown as the dashed line in Figure

1), a 5.6% non-wear time would result in reducing the protection factor to 17 which is a 18 fold

increase in exposure when compared to that being achieved when worn correctly. However, this

effect on protection is based on the worst case assumption that when the visor is lifted the

protection factor is equal to 1, which may not be the case if there is some residual protection

provided by the AFV even when the visor is in the lifted position.

1.3 STUDY AIM

The aim of the study was to determine the degree of potential exposure to an airborne

contaminant when the visor of an AFV is lifted and to explore potential engineering solutions to

reduce exposure during a visor lift.

The study has the following objectives:

Gather information relevant to visor lift by conducting informal interviews with paint

sprayers from the MVR trade.


result of a visor lift by conducting a series of tests using a dummy head and a breathing

machine using a range of AFV.

3


result of a visor lift by conducting a series of tests using volunteer test subjects using

two models of AFV.

Explore engineering solutions to enhance residual protection during a visor lift.

Develop an illustrative tool to demonstrate the effect of visor lift on protection provided

to the wearer.

Develop an exposure model for determining exposure or reduced protection given a

number of input variables including visor lift duration, visor lift frequency and wear

time.

4

2 IMPLICATIONS

This report describes the work undertaken to understand the effect on exposure of a wearer

lifting the visor of their AFV whilst still within a contaminated area, and to explore whether the

effect of exposure can be mitigated by the application of simple engineering modifications to

the AFV.

When used correctly, AFV can provide adequate protection preventing inhalation of isocyanates

as shown from previous workplace and laboratory studies and also from tests conducted in this

project using a harmless test aerosol. However, the lifting of the visor whilst still in a

contaminated area can place the wearer at risk of exposure to isocyanates.

One of the questions which is addressed by this project is to understand whether there remains

any residual protection offered by the AFV when the visor is in the lifted position. Does the

period during which the visor is lifted equate to a period of non-wear in which it is assumed that

the protection offered by the RPE is zero, i.e. a protection factor of 1?

The finding of the exposure tests using a dummy head shows that the residual protection offered

by the range of visor types tested when the visor of the AFV is in the lifted position is between

1 and 2.2. The visor designs which have the air flow inlet in the head-top providing an air flow

down across the wearer’s face returned residual protection factors slightly higher than those

designs where the air inlet is built into the chin area of the visor and is lifted away from the face

when the visor is raised. The latter design types are the most common models used in the MVR

trade.

During the visor lift the protection factor doesn’t instantaneously fall to the residual protection

factor, nor on replacement does it instantaneously return to the protection factor measured

immediately prior to the lift, and therefore the effect of the lift on the protection factor and thus

exposure is different to the residual protection factor. The protection factors measured during

the whole of the exposure period ranged from 1.4 to 9.0 (mean 2.7).

Testing has demonstrated that potential modification to the general AFV design can improve the

protection offered to the wearer during a simulated visor lift. A significant improvement in

protection is achieved when a clean air supply is maintained around the breathing zone of the

wearer. Within this project, an inner mask and a window slit configuration successfully

achieved this. However, in these configurations the wearer is still exposed to considerably more

contamination compared with when the AFV is used correctly.

5

3 MOTOR VEHICLE REPAIR BODYSHOP SITE VISITS

3.1 OBJECTIVES OF THE SITE VISITS

The purpose of the site visits was to gather information to inform the parameters to employ in

the laboratory exposure testing. There were three main objectives for the site visits:

i) To hold informal interviews with paint sprayers to gain a better understanding of the

frequency and duration of a visor-lift and duration and frequency of wear;

ii) To observe paint sprayers in order to understand the movements and work rates

involved; and

iii) To record the range of air-fed visors in use.

Additionally, the visits were seen as an opportunity to ask the paint sprayers about the problems

they experience when using their air-fed visor.

3.2 SETTING UP AND CARRYING OUT THE INTERVIEWS AND OBSERVATIONS

Semi-structured interviews were the preferred methodology for engaging with the paint

sprayers. The primary focus of the interviews was to elicit information from paint sprayers on

the practice of visor lifting, in the spray booth, during a painting session. However, as this visor

lifting behaviour contravenes good practice, and probably the employer’s health and safety

requirements, the research team concluded that the interviews would need to be conducted with

a degree of sensitivity in order to elicit honest responses from interviewees.

Given these sensitivities, the research team decided that:

The interviews would be conducted on a one-to-one basis, in a private room at the

sprayers place of employment;

Responses would be captured using written notes rather than audio recording; and

All interviewees would be asked the same questions, guided by a common question set.

A question set was developed (see Appendix A), and piloted on a paint sprayer working locally

to HSL. A number of minor changes were subsequently made as a result of the pilot.

All interviews were conducted in a private room, free from distractions. Written notes were

taken during each interview, and subsequently aggregated and analysed to produce an overall

impression of the practices and opinions of the paint sprayers. The paint sprayers were also

asked to make a subjective judgement of the perceived exertion required during paint spraying –

this was based on the Borg Scale of Exertion (Borg, 1982) – see Appendix A.

A second researcher from the HSL PPE Team visually examined the AFV in use at the sites and

engaged with management to discuss the RPE programme arrangements.

The findings of the site visits and interviews are reported in section 6.

6

4 AIR-FED VISOR TYPES INVESTIGATED

4.1 MODELS SELECTED FOR THE STUDY

From information provided by HSE, Ford Retail paint shop, the Vehicle Builders and Repairers

Association (VBRA) and from the information gained during the site visits the following

models were identified for the study:

Table 1 Air-fed visor models, types of face seal and associated APF

When tested for CE certification AFV must not exceed the maximum permitted level of inward

leakage at the manufacturer’s minimum design condition which can be either a minimum stated

pressure or air flow rate. For BSEN14594, (BSI 2005), Class 3A/3B devices and BSEN270

(BSI 2000) devices, the maximum inward leakage is 0.5%, (Nominal Protection Factor of 200),

and for BSEN14594 Class 4A/4B devices, the maximum inward leakage is 0.05%, (Nominal

Protection Factor of 2000). Model A was initially HSE approved to TM14/7.25 (HSE 1990) and

was required not to exceed the maximum permitted level of inward leakage of 0.5%, (Nominal

Protection Factor of 200).

Class A devices have less stringent mechanical strength requirements than class B devices.

4.2 DESIGNS OF AIR-FED VISORS

Air-fed visors generally follow the same basic design of a visor worn on the head with a

moveable full face shield with either an elasticated non-woven fabric type or closed-cell foam

type face seal that closes the gap between the wearer’s face and the edge of the visor.

Compressed air at a flow rate between 200 and 300 l/min (typically) and approximately 4 – 7

bar supply pressure (typically) is provided to the facepiece via a belt mounted air flow rate

control valve to provide protection against ingress of contamination. The belt mounted air flow

rate control valve regulates the air flow to a more or less constant flow rate over the range of

supply pressures. Where various manufacturers’ models differ in design is whether there is user

adjustment provided on the belt mounted air flow rate control valve and the design of air inlet

inside the visor. A typical design of an AFV can be seen in Figure 2.

AFV Model Type of face seal employed

Flow control valve

Certification APF

Model A Fabric N PPE Directive 89/686/EEC

40

Model B Foam N PPE Directive 89/686/EEC

40

Model C Fabric N BSEN14594 Class 4A

40

Model D Foam N BSEN14594 Class 4A

40

Model E Foam Y BSEN270 40

Model F Fabric Y BSEN14594 Class 3B

40

Model G Fabric Y BSEN14594 Class 3B

40

7

Figure 2 Typical design of an air-fed visor

Three models were fitted with user air flow adjustment. For Models A, B, C, D and E, the air

inlet inside the visor terminated in the chin area of the visor. Towards the end of the tube there

is a series of holes through which the air is directed into the visor. A foam sleeve which acts as

both an air diffuser and silencer is placed over the holes. See Figure 3.

8

Figure 3 Air inlet tube in Model A

In these models the air inlet is fixed to the lower part of the visor so that when this visor is lifted

away from the face the air inlet is also moved away from the wearer’s breathing zone. See

Figure 4.

When lifted, most of the air-fed visor’s visor moves to a position approx. 90o to the wearer’s

face. The visor on Model E lifts a little further than the others to approximately 110o relative to

the wearer’s face.

Figure 4 Photographs showing Model A and Model F air-fed visor in the lifted position

Ball probe sampling

at mouth of dummy

head

Foam inlet tube diffuser

9

Model F and G, which originated from a design of powered respirator and therefore share a

common head-top, employ a much larger air path to the visor. Both these designs comprise a

large bore breathing hose which routes the compressed air from the belt mounted air flow rate

control valve to the breathing zone over the top of the hood and down across the face of the

wearer. Therefore when the visor is lifted the air inlet remains in its original as worn position,

however the air path is obstructed to a varying degree by the fabric face seal of the visor when it

is in the lifted position. See Figure 5.

Figure 5 Model F air-fed visor showing the air inlet position

Air inlet

10

4.3 AIR FLOW MEASUREMENTS

The air flow rate into the air-fed visor over the range of manufacturers’ specified pressures was

measured. Where a belt mounted wearer-operated air flow rate control valve was fitted,

minimum and maximum flow rates were measured at the extreme of the flow adjustor settings.

The range of air flow rates used during the exposure tests ranged from 193 l/min to 325 l/min.

The flow rate for most devices that did not have a wearer-operated flow adjustor did not alter

significantly (typically < 200 l/min) over their specified input pressure range. The greatest

variation in air flow rate was obtained for devices that had a wearer-operated air flow adjustor,

with Model E having the largest range from 193 l/min to 325 l/min.

11

5 METHODOLOGY

A series of Inward Leakage (IL) tests using a salt aerosol challenge were carried out to

determine the protection offered by AFV devices during correct use and while in the lifted

position. The salt aerosol challenge concentration was approximately 10 + 2 mg/m3. This is

based on standard RPE test requirements (BSI 2001). The tests were carried out inside the PPE

IL chamber using a combination of dummy head non-breathing, dummy head with breathing

simulator and human subjects.

The downward air flow rate within the PPE IL chamber is approximately 0.4 m/s. This flow rate

is similar to the downward air velocity within a typical downdraught spray booth.

5.1 DUMMY HEAD NON-BREATHING

The AFV was fitted to the dummy head with the visor in the lifted position. Once the IL

chamber was filled with the required challenge aerosol concentration, the concentration at the

mouth of the dummy head was measured without the AFV operating. This is equivalent to a

situation of full exposure to the chamber challenge concentration. The AFV supply pressure and

flow settings were then adjusted as required and the challenge concentration at the mouth of the

dummy head measured. By comparing the ratio of the two measurements to the challenge

aerosol concentration the reduction in potential exposure provided by any residual protection

afforded by the air-fed visor in the lifted position can be determined.

The results are shown in Section 7.2.

5.2 DUMMY HEAD AND BREATHING MACHINE TESTS

The AFV was fitted to the dummy head with the visor in the down position and the air supply

pressure and flow settings were then adjusted as required. Once the IL chamber was filled with

the required challenge aerosol concentration, the challenge concentration outside the AFV and

the concentration at the mouth of the dummy head were measured – this gave a baseline

measurement. The visor was then lifted for the predetermined durations and an exposure

measurement was taken throughout the visor lift period and until the contaminant concentration

inside the visor returned to the within 80% of the baseline value.

The tests were conducted at breathing rates of 30 l/min and 40 l/min. There is no report of a

study in which the work rate of sprayers has been measured however, from the interviews with

sprayers most considered the work to be ‘light’ to ‘somewhat hard’ on the Borg scale.

According to BS 4275 (BSI 1997), (now superseded by BS EN 529 (BSI 2005a) - but the latter

does not contain work rate information), ‘light manual work’ is considered ‘low’ and with an

associated peak inhalation flow rate of up to 100 l/min which is equivalent to a sinusoidal

breathing rate of 30 l/min; and ‘sustained hand and arm work’ is considered ‘moderate’ and

with an associated peak inhalation flow rate of up to 150 l/min which is equivalent to a

sinusoidal breathing rate of approximately 40 l/min.

The visor can be lifted at any point in time throughout the breathing cycle. The data from the

scoping study showed that when the visor was lifted at the start of the inhalation phase, the

measured exposure was generally a little higher than when lifted at the start of the exhalation

12

phase. This was not unexpected as lifting the visor on inhalation will result in more complete

inhalations whilst the dummy head (‘wearer’) was exposed to the challenge concentration. For

the additional tests conducted, the lift was synchronised with the start of the inhalation phase.

The results are shown in Appendix B.

5.3 SIMULATED SPRAYING TESTS USING HUMAN SUBJECT TESTS

5.3.1 Purpose

To obtain a more realistic measurement of the effect a visor lift has on the protection provided

by the AFV, a series of exposure tests was carried out on human test subjects wearing an AFV

whilst inside the IL chamber using sodium chloride as the exposure challenge. The purpose of

running a series of tests on human test subjects was to determine the effect of the visor lift on

the protection offered to the wearer and therefore their potential exposure.

The results are shown in Appendix C.

5.3.2 Ethical approval

Project specific ethical approval was required for the human subject testing as the test protocol

required volunteers to deliberately lift up the visor of the AFV that they would be wearing

whilst inside the test chamber containing a test challenge agent of sodium chloride aerosol.

Ethical approval was obtained (ETHCOM/REG/13/04) and five volunteer test subjects were

recruited to participate in the study from the HSL PPE volunteer pool. The test subjects are

identified in this report as subject 1 through 5. The volunteers were assessed as medically fit to

take part in this study by HSL’s Centre for Workplace Health Unit. During testing each

volunteer had their heart rate monitored for the duration of the tests as a precaution against over-

exertion. A withdrawal criterion of the subjects’ maximum heart rate (185-age x 0.65) was used;

no subject had to be withdrawn.

5.3.3 Visor types employed in the human subject tests

The human subject tests were performed using Model A and Model F. Model A was selected as

this is the most commonly used model within the industry and is an example of the most

common air inlet position (in the area of the chin). Model F was selected as it was an example

of a device with the air inlet positioned at the forehead and from the knowledge gained from the

scoping study and from the dummy head/breathing machine tests Model F showed the highest

residual protection. This testing would give a comparison of the two different air inlet positions.

Five volunteer test subjects were tested inside the PPE IL chamber while wearing the selected

AFV models, a total of three times for each device. Whilst inside the IL chamber, the test

subjects carried out a walking exercise, two simulated spraying activities and a series of

simulated visor lifting activities.

13

5.3.4 Simulated spraying activity

From the data on work rate and from observations of spraying activities gained from the site

visits, two simulated spraying activities were designed:

Simulated spraying whilst standing, with sweeping arm movements at between chest

and head height (Figure 6a).

Simulated spraying whilst in a kneeling position with head lowered simulating spraying

a sill or wheel arch of a motor vehicle with head movement looking over shoulder to

both the right and left hand side (Figure 6b).

Figures 6a & 6b Examples of similar positions adopted during actual spraying (Figure 6b reproduced from Bolsover et al 2005)

5.3.5 Visor lift period

From the data gathered from the site visits the following visor lift periods were selected for use:

5, 10, 15, 20 and 25 seconds. The sprayers’ responses (n=20) to the question on the period of

visor lift ranged from 2 seconds to 30 seconds. Most responses on the maximum lift period were

10 seconds with just one of 30 seconds. It was decided not to use 2 seconds as this lift period

does not permit time for any degree of inspection and also it would be difficult measuring the

impact of a visor lift in this short duration. It was also decided not to use and 30 seconds as this

was only from a single response.

5.3.6 Simulated visor lift Following a measurement of the protection provided by the AFV during the two simulated

spraying activities, the volunteer was asked to stand breathing normally and then while holding

their breath, lift up the visor to simulate inspection of the sprayed item (Figure 7). After 5, 10,

15, 20 or 25 seconds, the volunteer replaced the visor to the normal position and breathed

normally for a further 60 seconds. Sampling continued before, throughout and after the visor lift

14

period thus providing a continuous measure of the protection factor. Before commencing the

next visor lift duration, the volunteer was asked to carry out approximately ten head up and

down movements and ten head side-to-side movements. The protection offered by the device

was not measured during these movements, the sole aim of which was to return the AFV and

more importantly the fabric face seal into its naturally resting position after the previous

simulated lift. This was repeated until all the visor lift durations had been completed.

Figure 7 Example of visor lift following spraying

(Photograph taken during simulated spraying)

5.4 VISOR IMPROVEMENT

The purpose of the visor improvement testing was to explore possible engineering solutions to

increase the residual protection offered by an AFV while in the lifted position. The concepts to

be investigated were:

Increased air flow.

Chin and forehead air inlet positions.

With and without the fabric face seal.

Slit in visor window.

Without visor screen.

Having an inner mask which stays in place when the visor is lifted.

Incorporating an air curtain as the inlet flow.

For all the AFV improvement tests, the modified AFV was fitted to the dummy head and the IL

chamber was filled to the required challenge aerosol concentration. The AFV was orientated and

operated on the breathing machine as described in the sections 5.4.1 to 5.4.6. The concentration

at the mouth of the dummy head was measured and gave the residual protection offered by the

AFV in the described orientation.

15

5.4.1 Increased air flow

With the AFV fitted to the dummy head and not connected to the breathing machine, and with

the visor in the lifted position, the supply pressure was regulated between the minimum and

maximum manufacturers operating pressures. To maximise the air flows, the belt mounted air

flow rate control valves were operated on the minimum and maximum settings. Model F and

Model E were used as they gave the greatest variation in air flows controlled by the belt

mounted air flow rate control valves. The maximum air flow was 325 l/min given by Model E.

To investigate the effect on higher flowrates, the head-top from Model F was connected to an

external blower unit and tested with flowrates of 200 – 500 l/min while fitted to a dummy head

with the breathing machine operating at 30 l/min.

5.4.2 Air inlet positions

Model A was fitted to the dummy head, not connected to the breathing machine and tested with

the air inlet located in the chin position (as originally supplied) and positioned across the

forehead (attached to the forehead cradle strap), see Figure 8. The tests were performed with

and without the fabric face seal in place. Model F was fitted to the dummy head and not

connected to the breathing machine.

Figure 8 Air inlet on forehead with and without fabric face seal

5.4.3 Slit in visor window

A slit (approximately 145 x 50 mm) was cut from the front of Model A, located in front of the

eyes of the dummy head (Figure 9). The theory behind this idea was instead of lifting the whole

visor up, a small section of the visor could be opened which would still leave a considerable

portion of the visor in place to contain the air supply around the wearer’s breathing zone. It may

be possible to manufacture a window into the visor to allow this operation. The mechanics of

how the window could be manufactured was not investigated here, but simply the residual

protection offered by the AFV with the window slit open was investigated. This idea is based on

a product supplied to the German market by the manufacturer of Model E. It is not known how

widely this product is used.

Foam diffuser

over air inlet

16

Model A with the window slit in the visor was fitted to the dummy head and tested with and

without the breathing machine operating. The air inlet positions were varied between the chin

and forehead positions, and the supply pressure varied between minimum and maximum

manufacturer’s operating pressures.

Figure 9 Window slit with air inlet at chin

5.4.4 Without a visor screen

Model A was tested with the visor screen removed (Figure 10). This is similar to the window

slit but instead of lifting a small section of the visor, the entire visor screen could be lifted

leaving the frame work of the AFV and fabric face seal in place along with the air inlet. A good

analogy would be the visor on an open-faced motorcycle crash helmet. This would keep the air

inlet in position when the visor is lifted. The mechanics of how the visor screen could be lifted

alone was not investigated here, but simply the residual protection offered by the AFV with the

visor screen removed (to represent the screen in the lifted position) was investigated.

Model A with the visor screen removed was fitted to the dummy head and tested with and

without the breathing machine operating. The air inlet positions were varied between the chin

and forehead positions, and the supply pressure varied between minimum and maximum

manufacturer’s operating pressures.

17

Figure 10 AFV without visor screen

5.4.5 AFV incorporating an inner mask

The theory behind this idea was to have a loose fitting inner mask that remained in position

when the visor was lifted, therefore maintaining an enclosed area of breathable air around the

wearer’s breathing zone. Three different designs of inner mask were tested using Model A. One

was a simple loose fitting mask with two holes, one on either side, around the nasal area. This

inner mask design was chosen as the two holes provided a means for the air flow to exit the

inner mask. This was tested with and without the holes taped up, and with the mask edges taped

to the dummy head (to represent a tight fitting inner mask). The second type of inner mask was

a simple loose fitting mask with check valves. This was chosen as the check valves would limit

any contamination being drawn into inner mask during the inhalation cycle. The third type of

inner mask was identical to the first with the nasal holes taped up, but with larger bore supply

tubing so that higher flowrates could be achieved. The three designs of inner mask are shown in

Figure 11.

Model A incorporating an inner mask was fitted to the dummy head and tested with and without

the breathing machine operating. The set up was tested with different air flowrates into the inner

mask. With all three inner mask designs, the visor could be lowered, not completely, but to such

an extent that the fabric face seal could be located underneath the chin of the dummy head.

18

Figure 11 From left to right, inner mask 1, inner mask 2 and inner mask 3

5.4.6 Air curtain flow pattern

The idea was to adapt the air inlet to provide a curtain of air across the wearer’s breathing zone

instead of the standard air inlet which distributes the air in all directions. A different air supply

tubing was used inside Model A, with a slit cut along the length below the breathing zone. To

direct the air flow towards the breathing zone of the dummy head, a portion of the slit was taped

up. See Figure 12. This set up was tested with and without the foam diffuser and at the

manufacturer’s maximum and minimum operating pressures. Model A with the window slit and

no visor configurations were tested with the air curtain flow pattern. Each set up was fitted to

the dummy head and tested with the breathing machine operating.

Figure 12 Air curtain configuration without foam diffuser

Slit cut into

breathing tube

19

6 MOTOR VEHICLE REPAIR BODYSHOP SITE VISITS

6.1 GENERAL

Six body shops were visited, ranging from a major vehicle manufacturing company to a small

family run firm. A total of 20 interviews were carried out by a human factors specialist.

Paint spraying was being conducted at four sites at the time of the visit, which permitted

observation by a second researcher. A further site set up a test piece so that spraying could be

observed. The spraying activities witnessed tended to be small pieces of work that required

short, but repeated spray coats. The paint sprayers were also asked to make a subjective

judgement of the perceived exertion required during paint spraying.

A summary of the main findings is given below with more detailed site specific information

given in Appendix A.

6.2 SUMMARY OF MAIN FINDINGS

In most cases, it was felt that the sprayers were honest and open and provided useful

information.

At one site, the sprayers were reticent and it was felt that they had been briefed by

management prior to the visit.

A majority of the sprayers (14/20) stated they lifted their visor during a period of spraying,

and before the booth had cleared, however no visor lifts were witnessed during the periods

of observation.

One sprayer was observed to remove their AFV whilst in the spray booth within one minute

after cessation of spraying and well before the required booth clearance time.

The period of visor lift ranged from 2 – 30 seconds, with a period of about 5 seconds

reported as typical.

Common reasons given for a visor lift were:

o Poor visual clarity of the visor;

o Over spray and a scratched visor;

o Working low down on a vehicle where the light is not as bright;

o Reflections due to lighting and booth wall construction; and

o Working with white and silver paints.

The typical number of times an AFV was worn during a shift ranged from 2 to 28, with

most of those who stated they lifted their visor saying that they would lift on average once

in each period of wear.

20

One site had purchased and put into use new air-fed visors just a couple of days prior to the

visit.

Generally, the site management (owner or body shop manager) were happy to talk about

their RPE programme, but the sprayers tended to only allow a quick look at their RPE.

In all cases the RPE was issued on an individual basis with the sprayers responsible for

maintaining their own kit. There was little evidence that the in-line filters in the air-fed

visors were being changed regularly.

Although most of the RPE seen were heavily used (apart from the site that had purchased

new RPE), it was generally in a condition that would provide a degree of protection. Faults

were found on four AFVs and these were brought to the attention of the management.

Generally, record keeping covering maintenance of RPE was poor or non-existent; however,

the major vehicle manufacturing sites did have reasonable record keeping.

All sites had regular spray booth clearance time checks and notices were posted on all spray

booths seen.

In a number of spray booths, the compressed air regulator and gauge were caked with paint

making it impossible to check the breathing air outlet pressure. No sprayer said that they

knew what the outlet pressure for the air-fed visor should be or checked it regularly. They

tended to assume the regular breathable quality checks (which in all cases were provided by

an external contractor) would ensure that the pressure and flows were set correctly.

One sprayer mentioned that the low flow warning whistle operated on occasions but he

didn’t know that this indicated a reduction in air flow rate to the visor.

Use of masking tape to seal the edges of the tear off visors, with the aim to keep the main

visor clean, was a common practice. This prevented wearers removing a splattered tear-off

visor during spraying.

Generally, there was a lack of training; instead, sprayers rely upon common sense and prior

employment experience.

Many sprayers had facial hair.

The perceived exertion during spraying ranged from ‘no exertion at all’ to ‘it is hard and

tiring but continuing is not terribly difficult’, but most perceived the exertion was in the

‘light’ to ‘somewhat hard’ range on the Borg scale.

Each time a sprayer exited the spray booth they disconnected the AFV from the air supply.

It was noted that this disconnection was not always at the exit but wherever the sprayer was

in the booth when he had completed the job. Therefore there was a potential for exposure

whilst walking to the exit.

21

6.3 IMPLICATIONS FOR MAIN STUDY

Exposure test should include measurements within the range of visor lift durations 2 to 30

seconds.

The breathing rates used in the scoping study, i.e. a breathing rate of 30 to 40 l/min

appeared to be in line with the work rate perceived by most sprayers and therefore will be

the choice of breathing machine setting in the main study.

Model A was the most common type of visor in use at the sites and was therefore selected

for inclusion in the main study.

22

7 TEST RESULTS

7.1 TERMS AND DEFINITIONS

Different terms are used to describe different periods during which the protection factor of the

AFV was measured and the way in which the protection factors are used.

Protection Factor: The value of the reduction in exposure calculated as a ratio of challenge

concentration (Co) outside the visor to the concentration measured at the mouth of the dummy

head or wearer (Ci):

Protection Factor = (Co)/(Ci)

Nominal Protection Factor: This is protection factor based on the maximum allowable total

inward leakage requirement of the European standard.

Assigned Protection Factor: Is the level of respiratory protection that can realistically be

expected to be achieved in the workplace by 95 % of adequately trained and supervised wearers

using a properly functioning and correctly fitted respiratory protective device and is based on

the 5th percentile of the Workplace Protection Factor (WPF) data (BSI 2005c).

Residual Protection Factor: This is the protection factor provided by the AFV when the visor

is in the lifted position under defined operating conditions.

Exposure Period: This is the period from the point of visor lift to the point after the visor

replacement where the protection factor has reached 80% of the protection factor before the

point of visor lift.

RPE Clearance time: Time from the point of the visor replacement to the end of the exposure

period.

Protection Factor During Exposure Period: This is the overall protection factor measured

during the exposure period. This differs from the Residual Protection Factor as it includes a

measure of the protection factor during the act of lifting the visor and during the RPE clearance

time.

Figure 13 shows the point of visor lift, point of visor replacement, the RPE clearance time, the

exposure period and the residual protection factor on a typical protection factor trace.

23

Figure 13 A plot of the typical effect on protection factor due to visor lift annotated with point of visor lift and replacement


Comparing the chamber challenge concentration and the challenge concentration measured at

the mouth of the dummy head during a visor lift, the reduction in potential exposure provided

by any residual protection afforded by the air-fed visor in the lifted position can be calculated.

Four measurements for each visor and for each setting were made.

The reduction in potential exposure is calculated using the equation below:

Reduction in potential exposure = Chamber challenge concentration

Challenge concentration measured at mouth

As RPE protection factors are calculated using the same parameters the reduction in potential

exposure is therefore the same as the protection factor measured for the RPE, therefore the

values for reduction in potential exposure shown in Table 2 can also be read as the protection

factor of the AFV when the visor is lifted, i.e. the residual protection factor.

24

Table 2 Mean residual protection factors when the visor is lifted

AFV Model Supply pressure

bar

User flow adjustment

(Max, Min, n/a)

Mean Residual

protection factor)

(n=4)

Standard deviation

Model A 4.2 n/a 1.6 0.2

Model B 4.2 n/a 1.4 0.5

Model C 5.2 n/a 1.5 0.4

Model D 4.8 n/a 1.5 0.7

Model E 4.4 Max 1.6 0.3

4.4 Min 1.6 0.1

Model F (air inlet towards visor) 4.0 Max 1.6 0.2

4.0 Min 1.6 0.3

Model F (air inlet towards face) 4.0 Max 2.1 0.4

4.0 Min 2.3 0.4

Model G 4.4 Max 2.0 0.3

4.4 Min 2.0 0.5

Overall protection factor (reduction in potential exposure) 1.7

n/a – no user adjustable flow control fitted


The results are shown in Appendix B, Table B.1. The exposures measured are presented as

protection factors which are based on the ratio of challenge concentration to the concentration at

the mouth of the dummy head, i.e. the contaminant concentration outside the AFV to that which

would be inhaled by the wearer. The values represent the protection factors measured over the

whole of the exposure period (see 7.1).

Results are shown for various durations of lift covering the periods 5, 10, 15, 20 and 25 seconds.

As expected, the longer the lift the higher the exposure and this applied across the range of

visors tested. (The tests for the visor lift duration of 25 seconds were additional to those

originally conducted as part of the scoping study, and were based on the feedback from sprayers

interviewed during the site visits).

For AFV with user adjustable flow control, tests were conducted at minimum and maximum

settings. As can be seen from the results, an increase in air flow rate generally reduced the

25

exposure (increased the protection factors); this effect can be clearly seen for Models E, F and

G.

The effect of increasing the air flow rate beyond the manufacturer’s range is explored in section

7.5.

7.4 SIMULATED SPRAYING TESTS USING HUMAN SUBJECTS

Measurement of the protection factor was made continuously throughout the simulated spraying

activities and visor lift periods.

During the visor lift the protection factor of the AFV doesn’t instantaneously fall to the residual

value, nor on replacement does it instantaneously return to the value prior to the lift, and

therefore the effect of the lift on the protection factor and thus exposure is different from

residual protection.

The residual protection factors and the protection factors during the exposure period (see 7.1)

for Model A and Model F are given in Tables C.1 to C.4 in Appendix C. The mean protection

factors when the visors were worn correctly were calculated from the results obtained during the

walking and simulated spraying activities.

The RPE clearance times for lift durations for Model A and Model F are given in Tables C.5

and C.6.

7.5 VISOR IMPROVEMENT TESTS

7.5.1 Initial testing

The development ideas were initially tested on a dummy head only, with no breathing machine

operating.

Model F was tested at the maximum (8 bar) and minimum (4 bar) supply pressures, and a

combination of maximum and minimum belt mounted air flow rate control settings. This

showed an insignificant difference between the maximum and minimum flow rates with

residual PFs of 2.4 and 2.3 respectively. Model E was tested in the same manner and showed no

difference between the maximum and minimum flowrates with a residual PF of 1.8 for both.

Model A was tested with the visor lifted, the air inlet position varied between the chin and the

forehead, and with a combination of with / without the fabric face seal. This showed an

insignificant difference with the residual PFs ranging from 1.6 to 3.0. Model F was tested with

the visor lifted and with / without the fabric face seal. This showed an insignificant difference

with the residual PFs ranging from 1.6 to 2.4.

Model A was tested with the visor down and with the window slit configuration. With the air

inlet positioned at the forehead, a PF of 783 was achieved with the maximum supply pressure

and a PF of 2157 was achieved with the minimum supply pressure. With the air inlet positioned

at the chin, a PF of 7438 was achieved with the maximum supply pressure and a PF of 8848 was

achieved with the minimum supply pressure.

26

Model A was tested with the visor frame in the lowered position but without the actual visor

screen in place. With the air inlet positioned at the forehead, a PF of 2.8 was achieved with the

maximum supply pressure and a PF of 2.7 was achieved with the minimum supply pressure.

With the air inlet positioned at the chin, a PF of 8168 was achieved with the maximum supply

pressure and a PF of 6951 was achieved with the minimum supply pressure.

Model A was tested with the inner mask 1 configuration at flowrates of 90, 125 and 155 l/min,

and with the visor in the down and lifted positions. This showed an insignificant difference with

PFs ranging from 12460 to 13297.

Model F was tested on a dummy head, operated on a breathing machine at 30 l/min, and with a

range of flowrates from 200 - 500 l/min. This showed an insignificant increase in residual PFs

of 2.6 to 3.1.

7.5.2 On dummy head with breathing machine

The development ideas were tested on a dummy head with the breathing simulator operating at

30 l/min. The protection factors were calculated based on the challenge concentration measured

at the mouth of the dummy head with the breathing machine operating at 30 l/min.

Model A with the inner mask 1 configuration was tested with flowrates of 90, 125 and 155

l/min. The PFs ranged from 7.5 to 49.0. With the holes at the nasal area taped over, three

separate tests were carried out with the PFs ranging from 21 to 14255, 18 to 4352 and 12 to 68.

With the holes at the nasal area taped over and the mask edges taped to the dummy head, the

PFs ranged from 147 to 15693.

Model A with the inner mask 2 configuration was tested with flowrates of 90, 125 and 155

l/min. The PFs ranged from 8.5 to 34.0. Model A with the inner mask 3 configuration was tested

with flowrates of 82, 120, 160, 195 and 215 l/min. Three separate tests were carried out with the

PFs ranging from 9 to 2445, 5 to 21 and 7 to 267.

Model A with the window slit configuration was tested with the maximum and minimum supply

pressures. Three separate tests were carried out with PFs of 2217 and 2191 respectively, 5458

and 5218 respectively and 1948 and 1969 respectively.

Model A without the visor screen in place was tested with the maximum and minimum supply

pressures. Three separate tests were carried out with PFs of 12 and 14 respectively, 7 and 7

respectively and 3 and 3 respectively.

Model A was tested using the air curtain inlet with the window slit and without visor screen

configurations:

Three separate tests were carried out using the window slit configuration and the air

curtain air flow without the foam diffuser at the maximum and minimum supply

pressures, with PFs of 1.1 and 1.1 respectively, 1.2 and 1.2 respectively and 1.1 and 1.2

respectively.

Three separate tests were carried out using the window slit configuration and the air

curtain air flow with the foam diffuser at the maximum and minimum supply pressures,

with PFs of 585 and 484 respectively, 390 and 537 respectively and 421 and 521

respectively.

27

Three separate tests were carried out using Model A without the visor screen in place

and the air curtain air flow without the foam diffuser at the maximum and minimum

supply pressures, with PFs of 0.9 and 0.9 respectively, 0.8 and 0.9 respectively and 0.8

and 0.9 respectively.

Three separate tests were carried out using Model A without the visor screen in place

and the air curtain air flow with the foam diffuser at the maximum and minimum supply

pressures, with PFs of 6.0 and 6.8 respectively, 5.1 and 6.3 respectively and 5.1 and 6.5

respectively.

28

8 DISCUSSION AND CONCLUSION


The findings of the exposure tests using a non-breathing dummy head, show that the residual

protection offered by the range of visor types tested when the visor of the AFV is in the lifted

position is between 1.4 and 2.3. When RPE is not worn the protection factor during the non-

wear period is assumed to be a PF=1. Although, these tests have shown that the residual

protection is greater than a PF=1, the maximum value measured of 2.3 still represents a

significant reduction in protection when compared to the APF of 40 assigned to this type of

RPE.

The visor designs which have the air flow inlet in the head-top providing an air flow down

across the wearer’s face returned protection factors slightly higher than those designs where the

air inlet is built into the chin area of the visor and is lifted away from the face when the visor is

raised. The latter design types are the most common models used in the MVR trade.

The fundamental difference between the above two described designs is that when the visor is

lifted the design where the air inlet is in the head-top remains in place and continues to provide

a curtain of air down across the wearer’s face. The protection offered by one type of AFV with

this design (Model F) was investigated further, see 8.4.


As identified in the dummy head non-breathing tests, the visor designs which have the air flow

inlet in the head-top providing an air flow down across the wearer’s face returned protection

factors generally slightly higher than those designs where the air inlet is built into the chin area

of the visor

The lower breathing rate of 30 l/min used during the tests does generally return a lower

protection factor than the results measured at 40 l/min. When in the lifted position the residual

protection offered by the AFV should not be affected by the breathing rate, however when the

visor is replaced a higher breathing rate flushed clean air through the system faster leading to on

average a slightly shorter RPE clearance time and a higher overall protection factor.

As expected, the longer the visor is in the lifted position the more time the residual protection

factor applies and this has the effect of lowering the overall performance of the AFV during the

total lift duration (exposure period). The mean PF for a 5 second lift was 3.7 which fell to 2.0

for a 25 second lift.

Whilst every effort was made to be consistent in the way in which the visors were lifted, the

synchronisation with the breathing cycle of the breathing machine and the duration of the lift,

there were inevitable differences due to the different design and construction of the AFV.

Together with the variation in the position of the fabric face seal when the visor was lifted, this

is likely to have contributed to the variation in the protection factors measured.

29

8.3 SIMULATED SPRAYING TESTS USING HUMAN SUBJECTS

A series of tests was carried out using two different AFVs; Model A and Model F, as these had

the air inlets positioned at the chin and forehead respectively. Each AFV was tested three times

using five human test subjects.

The testing has shown that when in the lifted position, there is very little difference in residual

protection obtained between the two air inlet positions (chin position on Model A and forehead

position on Model F) and both offer very little protection to the wearer. The mean overall

residual protection offered by Model A was 1.6 with a range from 1.0 to 3.7 and for Model F

was 1.8 with a range from 1.0 to 3.0. When worn correctly, Model A gave a protection of

>10000 for 13 out of 15 tests with the remaining 2 tests giving >6000, and Model F gave a

protection of >10000 for 8 out 15 tests with the remaining 7 tests giving >4000.

The protection factor during the total exposure period gave a similar comparison between the

two air inlet positions. The mean overall protection offered by Model A during the total

exposure period was 2.6 with a range from 1.4 to 6.2 and for Model F it was 2.8 with a range

from 1.5 to 9.0.

For each of the two AFVs tested, the duration of the visor lift made no difference to the

protection offered by the device during the lift period (residual protection), i.e. every visor lift

will give a reduction in protection to the same approximate level. However, a longer lift

duration will give a greater total exposure.

It should be noted that the lift duration varied between subjects. This was due to a combination

of how quickly the subject lifted and replaced the visor, how consistently the subject held their

breath, if the subject started to hold their breath after exhaling or inhaling and how effectively

the fabric face seal was replaced. These factors would give an estimated variation in lift duration

of + 2 seconds and would add variation to the calculated protection factors accordingly.

However, this variation is insignificant when comparing the protection factors when the visor is

lifted with when the AFV is worn correctly.

The RPE clearance time is the time from the point of the visor being replaced after a lift

duration to the point where the protection offered by the device has reached 80% of the

protection factor before the point of visor lift. The RPE clearance time gave a similar

comparison between the two devices and for each visor lift duration. The mean RPE clearance

time for Model A was 15 seconds with a range of 8 to 30 seconds. The mean RPE clearance

time for Model F was 16 seconds with a range of 11 to 27 seconds. Whatever the length of the

lift duration, the RPE clearance time of 15 - 16 seconds should be included to give the total time

of exposure to the wearer.

In conclusion, the results of the tests clearly demonstrate that lifting the visor whilst still within

a contaminated atmosphere significantly increases the wearer’s exposure. Given the fairly

common design across AFV manufacturers, the findings can be applied across all types of AFV.

8.4 VISOR IMPROVEMENT TESTS

Initial tests on the dummy head without the breathing machine operating demonstrated that

increasing the flow rate had no substantial effect on the protection offered by an AFV while in

the lifted position. Further testing with the breathing machine operating, again showed no

substantial increase in the protection offered, with an increase in flowrate of 200 – 500 l/min

only giving a protection factor increase from 2.6 to 3.1. Initial tests also indicated that when in

the lifted position, there is no substantial difference in protection offered by an AFV with or

30

without the fabric face seal in place, or with the air inlet positioned at the chin or forehead area

of the visor.

Testing of an AFV incorporating a loose fitting inner mask showed this concept to considerably

increase the protection offered by the device while in the lifted position. The testing suggests

the best configuration of inner mask is to have no holes around the nasal area and large bore

tubing so that higher flowrates can be achieved. The testing demonstrated that higher flowrates

gave more protection. However, the protection offered by the increased flowrate needs to be

balanced with wearer comfort as higher flowrates invariably give rise to wearer discomfort.

Taping the inner mask to the dummy head gave increased protection but replicated a tight fitting

inner mask. As a tight fitting inner mask was not desired, this was not pursued any further. All

three inner mask configurations gave variable results; the largest variation being the inner mask

1 with holes taped giving protection factors ranging from 14255 to 68, when tested at 155 l/min.

The variation can be attributed to how the inner mask was fitted to the dummy head. Even

though it was a loose fitting inner mask, the fit to the dummy head made a considerable

difference to the protection offered by the device. This variation in protection will need to be

considered if this concept is developed any further. The discomfort issue relating to the inner

mask concept and any resemblance to a tight fitting mask will also need to be considered.

Testing of an AFV incorporating a window slit showed this concept to considerably increase the

protection offered by the device in comparison with a lifted visor. The window slit

configuration was tested using the as received regulator at the manufacturer’s maximum and

minimum operating pressures which both give a flowrate of 218 l/min. This was consistent with

the invariable protection factors seen between the two operating pressures. The window slit

configuration gave more consistent results compared to the inner mask configurations

suggesting that this may be a more preferred option to develop further. The initial testing

demonstrated that the air inlet position gave higher protection when positioned at the chin rather

than at the forehead. When positioned at the chin, it is presumed the majority of the air passes

across the breathing zone and disperses out from the AFV through the window slit, compared to

when positioned at the forehead, the majority of the air disperses out through the window slit

before reaching the breathing zone.

The AFV configuration without a visor screen (similar to an open-faced motorcycle crash

helmet) did not provide an increase in protection. As the visor screen is not in place, it does not

retain the clean air around the breathing zone. This indicates that the ideal configuration to

maintain an adequate level of protection requires a means of containing the clean air supply

around the breathing zone. The testing demonstrates that the inner mask and window slit

configurations meet this requirement and should be investigated further.

The AFV without the visor screen and the window slit configurations were tested with the air

curtain development but did not provide any additional protection compared to the protection

offered when the visor is lifted. It is suspected that the air curtain configuration without the

foam diffuser created a venturi effect, creating a negative pressure and drawing the challenge

salt aerosol through the fabric face seal. The salt deposited on the fabric face seal close to the

inlet can be seen in Figure 14. When the foam diffuser was added, this increased the protection

but not to levels previously seen for the without visor screen and window slit configurations.

31

Figure 14 Salt deposits on fabric face seal during air curtain testing

8.5 ILLUSTRATIVE VISOR LIFT VIDEO TOOL

An illustrative visor lift video tool has been developed to demonstrate the effect of a visor lift. It

is intended that the tool will ultimately be made available for training purposes.

The illustrative video tool was developed to highlight the increase in wearer exposure when the

visor of an AFV is lifted whilst still within a contaminated area. The video shows a sprayer

applying ‘paint’ to a workpiece whilst wearing the AFV correctly, see Figure 15a. On

completion of a spray coat, the video shows the sprayer lifting the visor and examining the

workpiece, see Figure 15b. The sprayer then replaces the visor and applies a further coat of

paint. There is an on-screen graphical representation of the sprayer’s exposure together with a

colour change bar which, when green, indicates low exposure, i.e. good protection, and which

changes colour to red to indicate high exposure when the visor is lifted. The video tool graphical

representation of exposure demonstrates that the exposure is not instantly reduced when the

visor is replaced.

For the purpose of the video tool and the fact that the sprayer was requested to deliberately

exhibit poor practice and lift thus placing themselves at potential risk of exposure, water instead

of isocyanate paint was used.

32

Figure 15a & 15b Screen shots taken from the video tool. The inserted chart displays the measured exposure during a visor lift. The grey area is the time period of the visor lift and the bar chart shows green for low exposure changing to red to indicate higher

exposure.

33

9 REFERENCES

Bolsover JA (1996) Effectiveness of air-fed visors for paint spraying. HSE internal report

IR/L/PE/96/6

Bolsover JA, B Rajan-Sithamparanadarajah and N Vaughan (2006) Workplace protection of air-

fed visors used in paint spraying operations. Ann. Occup. Hyg. 50:219-229.

Borg GAV (1982) Psychophysical bases of perceived exertion. Med Sci Sports Exc 14 377

BSI (1997) BS 4275:1997 Guide to implementing an effective respiratory protective device

programme.

BSI (2001) BSEN 13794-1:2001Respiratory protective devices - Methods of test - Part 1:

Determination of inward leakage and total inward leakage

BSI (2005a) BSEN529:2005 Respiratory protective devices — Recommendations for selection,

use, care and maintenance —Guidance document

BSI (2005b) BSEN14594:2005 Respiratory protective devices — Continuous flow compressed

air line breathing apparatus - Requirements, testing marking

BSI (2005c) BSEN529:2005 Respiratory protective devices — Recommendations for selection,

use, care and maintenance — Guidance document

BSI (2000) BSEN270:1994 + A1:2000 Respiratory protective devices — Compressed air line

breathing apparatus incorporating a hood - Requirements, testing marking

Clayton 2013, Investigation into exposure to aerosols when the visor of an air-fed respiratory

protective equipment is raised during spraying of motor vehicles – scoping study.

PE/LET//13/15

HSE 1990 HSE standard for type approval of respiratory protective equipment; Air-fed visor

respirator, TM14/7.25.

HSE (2010) Table THORR06. Occupational asthma: estimated number of diagnoses in which

particular causative substances were identified. Reported by chest physicians to SWORD and by

occupational physicians to OPRA during 2007–2009

http://www.hse.gov.uk/STATISTICS/tables/thorr06.xls

HSE (2014) INDG388 (rev2) Safety in isocyanate paint spraying.

www.hse.gov.uk/pubns/indg388.htm.

Jones K. Cocker J and Piney M, (2012) Isocyanate exposure control in motor vehicle paint

spraying: evidence from biological monitoring. Ann. Occup. Hyg. doi:10.1093/annhyg/mes056

Sanders V, and Davies T, (2006) An Observational Study of Motor Vehicle Repair Paint

Sprayers HSL/2006/44. www.hse.gov.uk/research/hsl_pdf/2006/hsl0644.pdf

Vaughan N and Rajan-Sithamparanadarajah B (2005) Meaningful workplace protection factor

measurement: Experimental protocols and data treatment. Ann. Occup. Hyg. 49:549-561

http://www.hse.gov.uk/STATISTICS/tables/thorr06.xls

http://www.hse.gov.uk/pubns/indg388.htm

34

APPENDIX A- MOTOR VEHICLE SITES VISIT REPORT

A.1 Specific site visits details Site 1

Sprayers: Three sprayers. One sprayer had few days’ stubble; a second had light beard growth.

RPE: Pulsafe visors with elasticated fabric face face seal

Individual issued RPE.

Pressure to AFV not set with user using the pressure gauge on the gun to set the spray pressure

but assumes pressure at wall is OK. “Relies on a chap who comes every 6 month to check the

system”. Pressure gauges inside the spray booth coated with paint and gauges not visible. No

pressure or flow checks carried out. One wearer uses tape to seal the edges of the tear-off visors

to keep the main visor clean but has to come out of the spray booth to change the tear-off visor.

Having multiple tear-off visors causes greater distortion of vision.

Condition: Visor covered with paint and in a general poor condition with rips in the face seal

fabric.

Maintenance: Sprayers responsible for their own RPE. No records kept. The visor

filter/regulator completed caked with paint. Wearers said that the filter had been changed within

the last 6 months. No compressed air quality records available.

Storage: Visors stored in drawstring bag inside a drawer. Condition is dirty.

Other PPE: Coveralls/gloves worn whilst spraying.

Activity witnessed: Spraying of body panels on stands, sweeping arms movements, shoulder

height with bending to spray underneath the panels. Duration of spraying witnessed: 10 mins.

Spay booths: Booth clearance times posted on the doors: 1 min 45 sec; 2.00 mins.

Other information: Smell noticed when stood outside the booth doors. Lighting within the

spray booth and the colour/finish of the walls can impair vision further.

Site 2:

Sprayers: Two sprayers; one sprayer had few days stubbles and a second had light beard.

RPE: Devilbiss Pro-Visors and an older Pulsafe visor.


One sprayer did say that the whistle goes off occasionally when there’s demand on the system.

He did not know the purpose of the whistle.

Condition: The Pro-Visors were in fairly good condition. The Pulsafe was coated with paint

but otherwise appeared to be in a reasonable condition.

Maintenance: Sprayers responsible for their own RPE. The sprayers claimed to replace the

visor filter every 3 months. No records kept.

Storage: No specific storage area, visors kept on a work top at the rear of the spray booths.

Activity witnessed: No spraying witnessed during the visit.

Spray booth: Booth clearance times posted on the doors: each stated 2.00 mins. (11.1.13)

Other information: Respirator wear notices were posted on the booth doors.

Site 3:

Sprayers: Three sprayers. One sprayer had facial hair (substantial stubble).

RPE: Devilbiss visors MP623 .

The company had purchased new Devilbiss visors MP623 prior to our visit.

Breathable air supply pressure on the wall inside the booth was set to 5bar, however the gauge

and regulator were covered with paint making adjustment and reading difficult.


35

Condition: New RPE in good condition. One sprayer fetched his older kit which was also a

Devilbiss visor MP623. The low pressure breathing hose from the belt mounted air flow rate

control valve to the visor had been replaced and was fitted with a jubilee clip, otherwise

reasonable condition.

Maintenance: The bodyshop manager said RPE changed approximately every 6 months.

Records of RPE checks and replacement were available.

Air quality checked every 3 months and records kept.

Storage: Visors stored in drawstring bags inside a drawer. Relatively clean environment.

Spray booths: Booth clearance times posted on the doors: stated 2mins 15 sec, and 1min 15 sec

(tested 6.6.13). Booth temperature 29oC.

Activity witnessed: Spraying of car front wing and body panels on stands, sweeping arms

movements, shoulder height with bending to spray underneath the panels. Kneeling and

spraying. Duration approx. 5 mins/coat.

Other information: Sprayers complained of glare from the booth lights.

Site 4:

Sprayers: Three sprayers; one with facial hair.

RPE: Devilbiss MPV 623 x 3.


Condition: Reasonable condition but one device had a kink in the low pressure tube. Various

ages from 6 - 12 months.

Maintenance: The bodyshop manager said RPE changed as and when required. Records of

RPE checks and replacement were available. The sprayers had been given no training on how to

use or maintain their RPE. When asked they said they use common sense/had just picked it up

from others.

Storage: The RPE was kept in a drawer, relatively clean.

Activity witnessed: Spraying activities included kneeling and squatting. Witnessed 5 minutes

spraying of a front bumper - lots of sweeping arm movement at shoulder height.

Spray booths: Booth clearance times: 1m 15s last tested 22/4/13.

Other information: Sprayers complained of glare from the booth lights.

Site 5:

Sprayers: Four sprayers including one apprentice. Two sprayers wore beards.

RPE: Devilbiss MPV 623 with cloth face seal x 1, SATA x 2 and ANEST IWATA (new visor)


Condition: Both SATA devices heavily coated with paint. Their pressure gauges and flow

controls were visible and were working. The Devilbiss low pressure tube had been replaced and

was fitted with a jubilee clip, not as original design. One of the SATA devices had a broken clip

on the chin area of the visor surround which left a sizable gap between the face seal and the

wearer’s face; this was mentioned to the company contact. The IWATA was newish and was in

good condition.

The sprayers had been given no training on how to use or maintain their RPE. Bodyshop

manager said they can with the knowledge.

Maintenance: Sprayers look after their own kit. No records kept.

Storage: RPE stored in their original cardboard boxes which were reasonably clean.

Other PPE: Coveralls with hood worn.

Activity witnessed: Spraying of a test piece on a stand. Movement involved squatting, kneeling

and shoulder height arm movements.

Spray booths: Spray booth clearance times 3 mins (tested 7/3/13) and 2:30 (tested 7/3/13).

Compressed air quality checked every three months by an external service provider.

The pressure gauges in the spray booths were visible and were set to approx. 4-5 bar outlet

pressure.

36

Site 6:

Sprayers: Four sprayers.

RPE: Devilbiss MPV623 with cloth face seal x 2; Devilbiss MPV623 with foam face seal x1;

SATA airline half mask x1.


Condition: The foam face seal on the Devilbiss visor was showing signs of wear, otherwise the

RPE was in reasonable condition. The tear-off visors were taped to the main visor with masking

tape.

Maintenance: Records of RPE filter changes were kept and show a regular 3 monthly

replacement schedule. The sprayers had been given no training on how to use or maintain their

RPE. When asked they said they use common sense/had just picked it up from others.

Other PPE: Coveralls with hood worn.

Spray booths: Spray booth clearance time 2:30 mins and 3:00 mins. Booth temperature when

spraying 20-25oC.

Activity witnessed: One sprayer was applying multiple coats to a job. After finishing each coat

the sprayer walked towards the booth door, removed the visor and left the RPE on the spray

booth floor before exiting the booth. The removal of the RPE was <1 minute after cessation of

spraying.

Other information: Respirator wear notices were posted on the booth doors. HSE in a visit had

questioned the use of the air supplied half-mask and have required the firm to carry out urine

tests. The firm say they have all the sprayers tested and also include a lung function test.

Table A.1 Borg Scale of perceived Exertion - Summary of findings from the site visits (Ref: Borg,1982)

Borg Scale

Borg Description Common description of exertion

Number of responses

6 No exertion at all 2

7 Very, very light 2

8

9 Very light As for a healthy

person taking a short walk at own pace

2

10 2

11 Fairly light 3

12 3

13 Somewhat hard But still feel OK to

continue 3

14 1

15 Hard It is hard and tiring but

continuing is not terribly difficult

1

16 1

17 Very hard

It is strenuous. You can still continue but

you really have to push yourself

18

19 Very, very hard An extremely

strenuous level

37

Figure A.1 Air-fed Visor Interview Data Collection question set

We are doing some research for the Health and Safety Executive (HSE) to get a better

understanding of how air-fed visors (AFV) are used in the MVR industry. We’re not here

doing any kind of inspection, just gathering information.

We want to get some ideas for how we can improve how AFVs are used in the industry.

We are interested in finding out about how you use AFVs e.g. how often you wear them I

am conscious of time, so won’t ask you too many questions – how long can you spare?

Are you happy to answer a few questions?

1. For what task do you use your AFV? E.g. do you perform more than one type of spraying

task?

2. For how long do you wear the AFV without taking it off [during a typical spraying

session]?

3. How many times do you wear the AFV during a typical working day?

4. If you lift the AFV at any time to check the quality of your work, how many times do you

do this during a typical spraying session?

5. Do you do jobs where you need to lift your visor more often? [Probe: what are these jobs?]

6. For roughly how many seconds do you typically have your AFV lifted up? [Probe: Why for

X seconds?]

7. When your visor is lifted, do you breathe normally? Y/N

8. What sort of problems do you have with your AFV that requires you to lift it during a

spraying session? (e.g. seeing the job properly)

9. Do you have any ideas for improving the AFV so you would not have to lift it in order to

see the job better?

38

APPENDIX B – BREATHING MACHINE DATA

Table B.1 Breathing machine dummy head data

Face

seal

Type

Test

pressure

User flow

adjustment

Test

flow

rate

Breathing

rate

Lift

syncronised

with

Base

line

5 sec

Visor

Lift

10 sec

Visor

Lift

15 sec

Visor

Lift

20 sec

Visor

Lift

25 sec

Visor

Lift

bar l/min l/min~ PF PF PF PF PF PF

Fabric 4.8 Not fitted 218 40 - 5562 6.4 4.4 2.6 2.3

Fabric 4.8 Not fitted 218 30 Inh >10,000 6.3 3.6 2.8 3.0 2.5

Foam 4.8 Not fitted 218 30 Inh 9266 4.7 3.0 2.3 2.4 2.1

Fabric 5.4 Not fitted 280 40 - 5627 4.5 3.3 3.0 2.2




Fabric 5.4 Not fitted 280 40 Exh 3.0

Fabric 5.4 Not fitted 280 40 Inh 3.0

Fabric 5.4 Not fitted 280 30 Exh 4.4

Fabric 5.4 Not fitted 280 30 Inh 2.7

Foam 4.8 Not fitted 275 40 - 6300 3.2 2.7 1.8 1.7

Foam 7.4 Not fitted 288 40 - 6250 3.5 2.5 2.0 2.2

Foam 4.4 min 193 40 - 6468 3.3 3.1 1.5 2.0

Foam 4.4 max 325 40 - 5781 6.2 2.8 3.7 1.8

Foam 4.4 min 325 30 Inh >10,000 3.8 2.8 2.6 2.3 2.4

Foam 4.4 max 325 30 Inh >10,000 4.5 3.5 3.1 2.7 2.8

Fabric 4.0 min 220 30 Exh >10,000 7.1 4.7 4.7 3.8

Fabric 4.0 max 278 30 Exh >10,000 7.6 6.7 5.8 3.9

Fabric 4.0 min 220 30 Inh >10,000 4.2 3.5 3.5 3.5 3.3

Fabric 4.0 min 220 40 Inh 8991 4.9 3.6 3.9 3.6 3.2

Fabric 4.0 min 220 30 Exh >10,000 4.5 3.5 2.7 2.2

Fabric 4.0 max 278 30 Exh >10,000 5.1 3.3 3.2 2.7

Fabric 4.0 min 220 30 Inh >10,000 3.6 3.5 2.7 2.9

Fabric 4.4 min 218 40 - 5627 4.5 3.3 3.0 2.2

Fabric 4.4 max 258 40 - 8333 5.1 4.3 3.6 3.1

Fabric 4.4 max 258 30 Inh >10,000 3.4 2.6 2.2 2,1 2.2

>8000 3.7 3.0 2.5 2.4 2.0

* flow inlet in visor facing down over the face ** flow inlet in visor facing towards the visorBaseline - PF measured with the visor in the down position

Model

Model A

Model F **

Harmonic mean PF

Model G

Model E

Model D

Model B

Model C

Model F *

39

APPENDIX C – SIMULATED SPRAYING TEST DATA

Table C.1 Residual protection factors when the visor is lifted for Model A on human subjects

Subject Test

Mean PF when worn correctly

Residual Protection Factor

Visor lift duration (Seconds)

5 10 15 20 25

1

1 >10000 2.3 1.3 1.5 1.4 1.3

2 >10000 1.1 1.1 1.4 1.8 1.2

3 6522 1.1 1.0 1.0 1.0 1.7

2

1 >10000 2.0 1.9 1.7 1.8 1.7

2 >10000 1.9 1.9 1.4 2.4 1.2

3 >10000 2.1 3.7 1.5 1.0 1.2

3

1 >10000 1.7 1.3 1.5 1.2 1.4

2 >10000 1.8 1.6 1.7 1.4 1.7

3 >10000 2.0 1.8 1.4 1.7 1.5

4

1 >10000 2.3 1.8 1.9 2.0 1.5

2 >10000 2.4 1.8 1.7 2.5 2.7

3 >10000 1.8 1.3 1.2 1.2 1.9

5

1 >10000 2.2 2.0 2.2 1.6 2.2

2 6684 1.8 1.8 2.1 1.5 1.4

3 >10000 1.7 1.5 1.3 1.3 1.6

Harmonic mean 1.8 1.6 1.5 1.5 1.5

SD 0.4 0.6 0.3 0.5 0.4

Overall harmonic mean 1.6

Overall SD 0.5

Max 3.7

Min 1.0

40

Table C.2 Residual protection factors when the visor is lifted for Model F on human subjects

Subject Test


Residual Protection Factor


5 10 15 20 25

1

1 >10000 2.6 2.4 1.7 2.1 2.2

2 6369 1.9 1.5 1.6 1.6 1.8

3 4198 2.3 2.2 2.1 2.1 2.0

2

1 >10000 2.2 2.0 1.2 1.2 1.1

2 6521 1.0 2.0 1.8 1.9 1.8

3 >10000 1.4 1.5 1.0 1.4 1.3

3

1 8558 2.0 1.6 1.8 1.8 1.5

2 >10000 3.0 2.2 2.4 2.3 2.2

3 7338 2.4 2.2 2.0 1.9 1.9

4

1 >10000 1.2 1.4 1.3 1.6 1.3

2 9156 1.8 1.9 1.8 1.9 2.0

3 7790 1.7 2.4 1.9 1.6 2.0

5

1 >10000 2.0 2.0 1.7 2.0 2.1

2 >10000 1.6 2.2 1.8 1.7 1.6

3 >10000 2.0 2.2 2.1 2.0 2.3

Harmonic mean 1.8 1.9 1.7 1.8 1.7

SD 0.5 0.3 0.4 0.3 0.4


Overall SD 0.4

Max 3.0

Min 1.0

41

Table C.3 Protection factors during exposure period for Model A on human subjects

Subject Test


Protection Factor during exposure period


5 10 15 20 25

1

1 >10000 6.2 2.0 1.8 2.2 1.6

2 >10000 2.3 1.8 2.3 2.7 1.5

3 6522 2.7 1.7 1.5 1.4 2.3

2

1 >10000 5.6 4.2 3.1 2.6 2.3

2 >10000 4.0 3.5 2.6 2.7 1.7

3 >10000 6.1 6.1 3.1 1.4 1.8

3

1 >10000 4.8 2.5 2.5 1.8 2.1

2 >10000 5.0 2.5 2.6 1.9 2.6

3 >10000 4.1 2.7 2.0 2.1 1.7

4

1 >10000 5.6 4.4 3.4 3.5 2.5

2 >10000 5.2 3.9 2.9 3.7 4.0

3 >10000 3.2 1.9 2.0 1.6 2.2

5

1 >10000 6.1 4.6 3.9 2.7 3.5

2 6684 4.3 3.2 3.5 2.1 2.0

3 >10000 3.8 3.3 2.2 1.9 2.2

Harmonic mean 4.2 2.8 2.4 2.1 2.1

SD 1.2 1.2 0.7 0.7 0.7


Overall SD 1.3

Max 6.2

Min 1.4

42

Table C.4 Protection factors during exposure period for Model F on human subjects

Subject Test


Protection Factor during exposure period


5 10 15 20 25

1

1 >10000 9.0 4.3 3.0 2.9 2.9

2 6369 2.8 2.4 2.1 2.1 2.2

3 4198 3.8 3.1 2.6 2.9 2.5

2

1 >10000 4.7 3.9 1.9 1.6 1.5

2 6521 2.2 3.1 2.6 2.7 2.3

3 >10000 2.7 2.7 1.9 1.5 1.9

3

1 8558 5.3 3.0 2.9 3.0 2.2

2 >10000 7.8 4.0 4.6 3.5 3.0

3 7338 4.5 3.6 2.8 2.5 2.4

4

1 >10000 2.9 3.0 2.2 2.3 2.0

2 9156 4.3 3.2 3.2 2.6 2.6

3 7790 3.0 3.6 2.6 2.1 2.5

5

1 >10000 5.5 3.3 3.3 3.4 2.9

2 >10000 3.1 4.0 2.7 2.1 2.2

3 >10000 3.7 4.0 3.6 3.4 3.5

Harmonic mean 3.7 3.3 2.6 2.4 2.3

SD 1.9 0.5 0.7 0.6 0.5


Overall SD 1.2

Max 9.0

Min 1.5

43

Table C.5 RPE clearance times for Model A on human subjects

Subject Test RPE clearance time (seconds)


5 10 15 20 25

1

1 28 16 17 23 14

2 17 13 14 11 12

3 11 8 10 15 16

2

1 16 22 22 17 14

2 20 14 21 10 13

3 15 13 16 12 11

3

1 18 16 16 14 17

2 16 12 12 12 17

3 9 9 11 11 9

4

1 22 30 21 22 24

2 21 25 23 20 19

3 13 17 17 11 12

5

1 16 21 18 19 23

2 13 14 14 13 13

3 13 16 14 12 12

Mean 15.3 14.6 15.4 13.8 14.1

SD 4.8 5.9 4.0 4.3 4.3

Overall mean 14.6

Overall SD 4.7

Max 30.0

Min 8.0

44

Table C.6 RPE clearance times for Model F on human subjects

Subject Test RPE clearance time (seconds)


5 10 15 20 25

1

1 17 16 20 14 16

2 14 15 13 15 13

3 14 12 12 13 12

2

1 16 22 20 19 18

2 16 15 22 13 13

3 14 13 15 12 14

3

1 20 17 15 20 19

2 18 14 19 15 14

3 12 12 11 11 11

4

1 26 27 24 25 25

2 25 20 24 20 18

3 22 19 16 17 17

5

1 21 22 22 23 22

2 14 14 14 11 11

3 12 15 16 18 15

Mean 16.4 16.0 16.5 15.4 15.0

SD 4.5 4.3 4.3 4.3 4.0

Overall mean 15.8

Overall SD 4.2

Max 27.0

Min 11.0

Published by the Health and Safety Executive 08/15



RR1064

www.hse.gov.uk

Air-fed visors (AFV) are commonly used within the Motor Vehicle Repair (MVR) trade for protection against exposure to isocyanate paints. However, a common practice amongst paint sprayers is to flip up the visor of their AFV immediately after spraying to check the quality of the paint finish. This may be only for a few seconds but if repeated numerous times during a work shift, this could potentially result in a significant increase in exposure. The aim of this project was to determine the reduction in protection and thus potential increase in exposure when the visor is lifted and to explore potential engineering solutions (by modifying the AFV design) to prevent exposure during any visor lift.

The results clearly demonstrate that lifting the visor whilst still within a contaminated atmosphere had a significant detrimental effect on the protection afforded by the AFV. Mean protection factors were measured at 1.7 in the lifted position and at 2.7 over the whole of the exposure period (from start of the lift to recovery of protection after refitting). This latter figure equates to a 15 fold increase in exposure when related to the assigned protection factor of40 for AFV when used correctly.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.

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