element b4 / 2 strategies and methods for sampling … · occupational hygienist role work at...

Element B4

Element B4 / 2

Strategies and Methods for Sampling and

Measurement

Atmosphere

Relatively fixed composition

78.09% Nitrogen

20.95% Oxygen

0.93% Argon

0.03% Carbon Dioxide

Also insignificant amounts of Neon, Helium, Krypton,

Hydrogen, Xenon, Ozone.

Any of these gases in greater proportion or any other

substance present is regarded as a contaminant.

Element B4

Occupational Hygienist

Role

Work at interface of people and workplace.

Use science and engineering to prevent ill health

Assessment and control of risks

Help employers and employees understand these

risks and to minimise or eliminate them

Identify, measure, assess and control atmospheric

contaminants.

Develop contaminant sampling strategies

May be involved in in house strategies

Element B4

Occupational Hygienist

Competence

MHSWR Reg 7 applies (Assistance)

BOHS

British Occupational Hygiene Society

Their reports

Ensure strategy, methods, approach are suitable

Results should be valid, reliable

Measurements should be representative of actual risk

Element B4

Monitoring Strategy

HSG 173

Important to know particle size

Element B4

Monitoring Strategy

Small particles less than 10 microns = slow falling velocity Remains in atmosphere with little or no air movement

Occ. Hygiene sampling – interested in total inhalable dust and respirable dust

COSHH 2002 “substantial concentration of dust” 10mg/m3 TWA 8 hrs total inhalable dust

4mg/m3 TWA 8 hrs respirable dust

* not for dusts assigned OEL or classified as Toxic, very toxic, harmful, corr, irr. Also not for lead or asb.

Element B4

Monitoring Strategy

HSG 173 – Methodology

3 stage strategy

Initial appraisal

Basic survey

Detailed survey

Also re-appraisal, routine monitoring

Element B4

Monitoring Strategy

Initial Appraisal

To establish need and extent of monitoring required

To provide info – types of hazards, potential risks

ID need for further info

Info gathered on substances, hazards, physical prop,

airborne forms

Element B4

Monitoring Strategy

Initial Appraisal

Info required:

Controls already in place

Duration / pattern of exposure

Individuals and groups of workers likely to be exposed

Number, type, location of sources

Work conducted where exposures likely

Working practices that influence exposure

RPE and any other PPE

WEL’s (EH40) related to the substance

Element B4

Monitoring Strategy

Initial Appraisal

Simple methods then used to determine extent of risk

Qualitative tests:

Smell – indicator of contamination (unreliable)

Smoke tubes – highlight air movement

Draughts, general or LEV

Dust lamp (Tyndall Beam) – fine airborne particles visible

Based on info established, may be decided level of exposure

relating to inhalation is acceptable.

If so, carry out exposure monitoring

Review need for monitoring as necessary – levels of exposure

can change

Element B4

Monitoring Strategy

Basic Survey

If initial survey suggests that:

Risk remains uncertain

New process introduced

New WEL or in-house std has been set

Significant changes since last assessment

Unusual work activities that may influence exposure are

planned

Provides an estimation of personal exposure

Indication of effectiveness of controls

Element B4

Monitoring Strategy

Basic Survey

ID employees at most significant risk

Semi quantitative methods

Stain indicator tubes – rough numerical estimate of exposure

More complex methods

Computer exposure modelling

Organic vapour analysers

Validated lab based sampling and analytic techniques

All require specialist knowledge

Element B4

Monitoring Strategy

Basic Survey

Simple measuring instruments

Air velocity meters to assess LEV

Qualitative methods used in initial appraisal

Can be used again

Element B4

Monitoring Strategy

Basic Survey

May be concluded that controls are acceptable

May ID limitations

If uncertain –

Direct action to control exposure OR

Carry out detailed survey and remedial action as necessary

Element B4

Monitoring Strategy

Detailed Survey

Required when:

Basic survey not adequate

Unexplained difference in measured exposure of employees

doing different tasks

Exposure to carcinogenic (R45) or resp sens (R42) is

involved

Initial and basic survey indicate that

TWA is close to WEL

Costs of improvements needs further justification

Work involves complex processes

Major maint or decommissioning of plant

Element B4

Monitoring Strategy

Detailed Survey

Likely to involve techniques used before together with more detailed monitoring

Requires more in depth assessment: Controls in use and suitability

Health Surv results

Info, Inst, Training provided

Maint procedures

PPE provided

Previous monitoring results

Work practices

Element B4

Monitoring Strategy

Detailed Survey

Requires persons conducting to have more specialist

knowledge.

For certain substances, detailed survey may need to

include use of biological monitoring

Element B4

Monitoring Strategy

Re-Appraisal

Once remedial action ID’d has been carried out

If risks high – additional monitoring required

Carcinogens are used

Patterns of exposure are very variable

Element B4

Monitoring Strategy

Routine Monitoring

When risks adequately controlled

Set up in order to ensure controls remain effective

COSHH mandatory REG 10

More cost effective to invest on better controls to reduce need for monitoring

Compare with previous results – monitor progress

Frequency will depend on level of risk, degree of control, changes in work practices

Element B4

Standard Methods (MDHS Series)

Methods for Determining Hazardous

Substances (HSE)

Advice on general methods of monitoring

Consult to ensure doc’s are current.

Lists hazards and category, along with recommended

methods of monitoring for each kind of substance

Element B4

General Methods for Sampling

Sampling techniques

Sampling is continuous or intermittent sampling of air

in working environment with a view to detecting

presence of contaminants

Can be undertaken on a long term or short term basis

Element B4


Sampling techniques

Short Term

“spot”, “snap” or “grab” sampling.

Takes an immediate sample of air and passes it through

particular chemical agent which responds to chemical being

monitored.

Or uses direct reading instrument to determine concentration

in the air

Element B4


Sampling techniques

Long Term

Personal samplers

Devices attached to person

Gas monitoring, filtration devices, impingers (limit devices)

Static sampling systems

Stationed in the work area. Sample continuously over time

(8hours) or longer if necessary. Mains or battery powered.

Element B4


Considerations

When deciding appropriate sampling method

Type of air contamination Review of materials, process, op procedures. SDS. Initial

Appraisal.

People affected Large group – random sampling. Representative selection.

Frequency of measurement Depends on hazard – acute or chronic, exposure limits,

previous results

Technique Based on hazard presented and purpose of sampling

Element B4

Gravimetric Analysis of Dust

General approach

4 factors influence sampling and

analysis methods

Nature of dust

Particle size

Exposure time

Airborne concentration

Element B4


Nature of Dust

Particle size

Critical – which particles will settle in the lung

Larger particles – bronchi and bronchioles

Inspirable particles

Smaller – alveolus

Respirable particles

Inhalable dust

Hazardous anywhere in respiratory tree

Element B4


Duration of exposure

Acute

Minutes, hours, no longer than day or two at most

Chronic

Months, years, lifetime

Sub-chronic

Days to weeks

Lead

Chronic lung conditions

Mesothelioma

Element B4


Concentration of dust in breathing zone

Breathing zone = hemisphere of 300mm radius in

front of face

Measured from mid point between ears

Element B4


Typical Filtration Sampling System

Element B4

FILTER SAMPLING

HEAD



Filter diameter, type, pore, size depends on dust

being sampled

TUBING PUMP



Element B4

FILTER SAMPLING

HEAD



Filter holder – several types depending on orientation

or wind speed

TUBING PUMP



Element B4

FILTER SAMPLING

HEAD



Length and diameter appropriate for sample – smooth

flow of air

TUBING PUMP



Element B4

FILTER SAMPLING

HEAD



Capable of maintaining smooth flow, specified rate.

Personal sampling – must be light and portable

TUBING PUMP

element b4 / 2 strategies and methods for sampling … · occupational hygienist role work at...

Documents