conditioning air filters with ipa vapor -...

Conditioning Air Filters with IPA Vapor

NAFA TECH2012 Phoenix, AZ

April 19, 2012

Monroe A. Britt

Green Leaf Technologies

[email protected]

HVAC General Ventilation Air Filters

Medias used in air filters may contain an electrostatic charge

Charged medias may cause increase in particle size efficiency

Charged medias may decrease in efficiency over time

• charge may dissipate

• charge may become masked by dust particles

Installed filter may not be providing degree of protection as believed by user and required for intended purpose

Possible Causes for Reduced Filter Efficiency

High humidity

Sensible moisture

Elevated temperature

Atmospheric dust particles

• Cigarette smoke

• Diesel fume

Atmospheric aerosols

• Cooking oil

• General hydrocarbons

Etc. Etc, Etc

Not all charged medias response to all contaminants to same degree

Recommended Reference

ASHRAE Research Project ---- RP 1189

“Investigation of Mechanisms and Operating Environments that Impact the Filtration Efficiency of

Charged Air Filtration Media”

VTT Technical Research Centre of Finland VTT Industrial Systems

Matti Lehtimaki – Chief Research Scientist

Why “Condition” Filters?

To provide lab test results that better conform to “real life” service performance ---- better “apple-to-apple” comparisons

Same filter performance can vary greatly from site to site No one lab test method can accurately predict filter “real life” service

performance --- true for charged or un-charged medias User of filter should be made aware of the possibility of efficiency decrease and

to what extent would be expected under typical severe environmental conditions

Air filter laboratory test methods require COMPROMISE

Current Methods of Conditioning Air Filters

• ASHRAE 52.2 -- Informative Appendix J

Conducted on full size filters and establishes MERV A ranking and MERV A Dust Holding Capacity

• EN 779 -- conducted on flat sheet media or filter section , presently test data not used to assign G and F numbers

ASHRAE 52.2 KCl Conditioning Procedure

• Feed very large concentration (106 particles/cm3) of very fine KCl particles (less than 0.1 microns) until:

a. Efficiencies meet “convergence”

criteria (<2% difference in two adjacent bands), or

b. Total “particle concentration times

time” (CT) reaches pre-determined

limit (109 particles/cm3 – minute)

• Some filters may require over 24 hours of conditioning

Laskin Nozzle Sub-micron Particle Generators

Laskin Nozzle Particle Injection Into Duct

Condensation Particle Counter

Typical Conditioning Curves

EN 779-2011(E) Method of Discharge

Sample -- Flat Sheet or section of air filter

No. of samples --at least three, each with minimum area of 600 cm2 ( 93 in2)

Measure efficiency of samples at nominal velocity of 100% and 50%

Immerse in liquid isopropanol alcohol (IPA) for two minutes ---- 99.5% IPA

Place wet samples on perforated surface for drying – 24 hours - weigh after to insure samples are dry

Measure efficiency of conditioned samples at nominal velocity of 100 % and 50%

EN 779-2011(E) Influence of Discharged Flat Sheet Efficiency

IPA Vapor Conditioning of Air Filters

• ISO TC 142 WG9 --- Test Standards for Gas Turbine Intake Air Filter

• First proposed for flat sheet media conditioning method

• “Proposal on new preconditioning method”, Y. Ogaki, Japan Delegate

• “Comparisons of the dipping and fumigation methods for the discharge of electrets filtration media”, J. Cai, China Delegate

Proposed flat sheet IPA vapor method

Flat Sheet IPA vapor exposure and immersion

ISO TC 142 WG9 “Round Robin” Tests

• WG9 conducted flat sheet round robin test program

• five medias

• immersion and vapor

• 8 labs

• good agreement between labs

• IPA vapor efficiencies slightly lower than immersions.

Report --- “ISO TC 142/WG9 N91 Report on Round Robin test for IPA Methods”

Small IPA Vapor Chamber – with residential filter

Residential Filter– Small Chamber

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KCL Mean Particle Diameter - Microns

Filter Efficiency vs KCl Particle Size

New Filter 2.5 Hrs IPA Vapor Exposure

4.5 Hrs IPA Vapor Exposure 6.5 Hrs IPA Vapor Exposure

After Liquid IPA Dip

Fiber-Glass Rigid Filter – Small Chamber

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New Filter 1 Hr IPA Vapor Exposure

3.5 Hrs IPA Vapor Exposure

Synthetic Rigid Filter – Small Chamber

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New Filter

1 Hr IPA Vapor Exposure

3.5 Hrs IPA Vapor Exposure

Effect of IPA Chamber Size on Discharge

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New Filter

1 Hr IPA Vapor Exposure - LC


1 Hr IPA vapor Exposure - SC

3.5 Hr IPA Vapor Exposure - SC

IPA Chamber with 24 x 24 x 22 Pocket Filter Installed with 12 v dc fan

Pocket filter is companion filter to the pocket filter used in initial IPA vapor testing.

Previous tests proved that filter did not discharge when placed in large chamber(LC).

Filter did discharge when folded and placed in small chamber(SC)

Pocket filter Initial efficiency tested prior to IPA exposure

Filter placed in IPA vapor chamber for 1 hour with circulating fan operating

Comparisons of Pocket Filter Test Data Using Large and Small Chambers with and w/o Circulating Fan.

New companion filter (made at same time as previous filter) did have slightly higher efficiency than previous filter.

This chart demonstrates that the previous pocket filter did not discharge in the large chamber (LC) with out a circulating fan.

The discharge of the companion filter that are discharged in the large chamber with the fan matches the discharge data of the previous filter placed in the small chamber.

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New Filter



1 Hr IPA vapor Exposure - SC

3.5 Hr IPA Vapor Exposure - SC

New Companion Filter

Companion Filter - 1 Hr IPA Vapor LC w/Fan

IPA Vapor Chamber with 12v dc Fan Installed -- with 3 20 x 20 x 1 filters Each filter tested in 52.2 test duct for Initial efficiency prior to IPA exposure 99.% IPA liquid added to cover bottom of chamber 4 inch x 4 inch fan turned on and filters exposed to IPA vapor for 1 hour.(note fan toward bottom left inside of chamber) Fan free airflow is approximately 80 cfm Chamber volume is approximately 35 cubic feet Caution -- Use of Electric Fans and IPA/Air Mixtures Can Potentially Cause Explosions. Consult your Safety Officer and Company Policies

Initial Efficiencies of the 3 Filters before and After IPA Exposure Efficiencies of 3 filters in good agreement prior to IPA vapor exposure

After exposure, three filters have significantly different efficiencies. Resistances of filters did not change.

Filters were relocated in chamber (move middle to bottom, bottom to top, and top to middle) and IPA vapor exposure and tests repeated.

Location of filters within chamber had no effect on the results

Test Program repeated to verify conclusion.

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KCl Particle Size - Microns

KCl Particle Size Removal Efficiency

Filter A - New Filter B - New

Filter C - New Filter A - Bottom - IPA

Filter B - Middle - IPA Filter C - Top - IPA

Initial Efficiency of Pocket Filter Prior to and After 1 Hour IPA Vapor Exposure with Fan

Pocket Filter did demonstrate significantly lower efficiencies after IPA vapor exposure in large chamber with air circulating fan.

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KCl Particle Size - Microns

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1 Hr IPA Vapor with Fan New Filter

Caution -- Use of Electric Fans

and IPA/Air Mixtures Can

Potentially Cause Explosions.

Consult your Safety Officer and

Company Policies

IPA Vapor Chamber with 12v dc fan Installed -- with 2 20” x 20” x 1”

filters

Each filter tested in 52.2 test duct for Initial efficiency prior to IPA exposure 99.% IPA liquid added to five (5) round trays at top of chamber. No IPA liquid in bottom of chamber. Condition 1. Filters exposed to IPA vapor for one hour with out fan operating; efficiency measured on both filters. Condition 2. Filters exposed to IPA vapor for an additional hour with fan operating; efficiency measured on both filters Condition 3. Filter located on bottom dipped in liquid IPA for two (2) minutes; efficiency measured on filter Caution -- Use of Electric Fans and IPA/Air Mixtures Can Potentially Cause Explosions. Consult your Safety Officer and Company Policies

Initial Efficiencies of the 2 filters before and after IPA exposure - w & w/o fan

Efficiencies of the 2 filters in good agreement prior to IPA vapor exposure

Condition 1. Exposure w/o fan; neither filter efficiencies were affected by IPA vapor

Condition 2. Exposure with fan; both filters affected by IPA, essentially to the same degree;

Condition 3. Bottom filter dipped in IPA liquid; filter affected to the same degree as in previous tests

Items to Resolve

Apparent simplicity and low cost of IPA vapor method

warrants further study

• Safe use of electric fan in IPA vapor/air mixture

• Proper design of IPA chamber with and without fan to re-circulate air

• Period of time for IPA vapor exposure for various style filters and medias

• Correlation of medias lab discharge vs field services

• Suggestions welcomed

Continued Verification of IPA Vapor Method

• ASHRAE 52.2 has formed Task Group to review status and recommend next actions.

• ISO TC 142/WG9 in process of round robin test program using full size filters

• ISO TC 142 WG3 has initiated process for approval to develop an ISO standard for conditioning full size air filters using the ISO vapor method.

List of Desirables

• Direct comparison data of lab IPA vapor results vs Appendix J method

• SEM Photo’s of various filter media fibers exposed to IPA vapor and IPA liquid

• Explanation of why IPA vapor “works” ,its limitations and potential problems

• Compilation of data on field service filters, IPA vapor, and IPA liquid

• Suggestions welcomed

conditioning air filters with ipa vapor -...

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