Filter Efficiency and Facial Filter Efficiency and Facial Fit of Health Care MasksFit of Health Care Masks

Lisa M Brosseau, ScD, CIHLisa M Brosseau, ScD, CIHAssociate ProfessorAssociate ProfessorUniversity of MinnesotaUniversity of Minnesota

AcknowledgementsAcknowledgements

Tara Oberg, MS, 3M CompanyTara Oberg, MS, 3M CompanyDan Dan JapuntichJapuntich, PhD, 3M Company, PhD, 3M CompanyKaren Karen CutaCuta, MS, 3M Company, MS, 3M Company

Surgical MasksSurgical Masks

Developed in early 1900sDeveloped in early 1900sUsed to prevent contamination of the Used to prevent contamination of the surgical fieldsurgical fieldUses have expanded to include Uses have expanded to include protection of the wearer from:protection of the wearer from:–– Splashes and sprays of body fluidsSplashes and sprays of body fluids–– Laser Laser ““plumesplumes””–– Dental aerosolsDental aerosols

Are Masks Effective?Are Masks Effective?

Can reduce dispersal of organisms from the Can reduce dispersal of organisms from the wearer and lower rate of bacterial wearer and lower rate of bacterial contamination in operative fieldcontamination in operative fieldNo correlation between wound No correlation between wound contamination and airborne bacteriacontamination and airborne bacteriaClinical studies show no difference in Clinical studies show no difference in surgical wound infection rates with or surgical wound infection rates with or without maskswithout masks

FDA Approval to MarketFDA Approval to Market

PrePre--market notificationmarket notificationApproval for marketing Approval for marketing –– not not certificationcertificationMask must be at least as good as Mask must be at least as good as anything currently on the marketanything currently on the marketASTM F2100ASTM F2100--0404 Standard Specification Standard Specification for Performance of Materials Used in for Performance of Materials Used in Medical Face MasksMedical Face Masks

ASTM F2100ASTM F2100--0404

ATSM F2100ATSM F2100--0404

Medical mask selection depends on exposure hazards– General use masks

Minimal fluid resistanceIsolation settings

– Sub-micron masksLaser or electrocautery surgery

– Fluid-resistant masksProbability of exposure to blood or body fluids

ASTM 2100ASTM 2100--0404

Does not evaluate medical face masks for regulatory approval as respiratorsOnly evaluates materials used in the construction of medical face mask --not the seal against the wearer’s face or other design features that determine its effectiveness of preventing exposure to the wearer

ASTM 2100ASTM 2100--0404

Test Methods– Bacterial Filtration Effıciency—ASTM F 2101– Differential Pressure—paragraph 4.4.1.2 of MIL-

M-36954C– Sub-Micron Particulate Filtration—ASTM F 2299– Resistance to Penetration by Synthetic Blood—

ASTM F 1862– Flammability—16 CFR Part 1610

ASTM 2100ASTM 2100--0404

Submicron Particulate Filter Efficiency (PFE)Submicron Particulate Filter Efficiency (PFE)–– F 2299 Test Method for Determining the Initial F 2299 Test Method for Determining the Initial

Efficiency of Materials Used in Medical Face Efficiency of Materials Used in Medical Face Masks for Penetration by Particulates Using Masks for Penetration by Particulates Using Latex SpheresLatex Spheres

Bacterial Filtration Efficiency (BFE)Bacterial Filtration Efficiency (BFE)–– ASTM F2101ASTM F2101--01 Standard Test Method for 01 Standard Test Method for

Evaluating Bacterial Filtration Efficiency of Evaluating Bacterial Filtration Efficiency of Surgical Masks Using a Biological Aerosol of Surgical Masks Using a Biological Aerosol of Staphylococcus aureusStaphylococcus aureus

–– Also MilAlso Mil--MM--36954C and Modified Greene and 36954C and Modified Greene and VesleyVesley MethodMethod

SubSub--Micron Particulate Micron Particulate Filtration EfficiencyFiltration Efficiency

Uses 0.1 Uses 0.1 µµm latex m latex spheres spheres (monodisperse)(monodisperse)Flow rates from 0.5 to Flow rates from 0.5 to 25 cm/s25 cm/sCount particles Count particles upstream and upstream and downstream using light downstream using light scattering photometerscattering photometer

KEY POINTS:

• Aerosol not neutralized

• No standard flow rate

Bacterial Filtration Bacterial Filtration EfficiencyEfficiency

Staphylococcus aureusStaphylococcus aureus, , average diameter 0.8 average diameter 0.8 µµm m (liquid dispersion)(liquid dispersion)Aerosol Aerosol size 3 size 3 ±± 0.3 0.3 µµmm66--stage Andersen stage Andersen impactorimpactor1 CFM (28.3 L/min)1 CFM (28.3 L/min)Challenge concentration: Challenge concentration: 17001700--2700 colony2700 colony--forming unitsforming units

KEY POINTS:

• Aerosol not neutralized

• Large particle size

• Counting colonies

Respirator Filter Respirator Filter Performance (42 CFR 84)Performance (42 CFR 84)

NIOSH certification tests use NIOSH certification tests use NaClNaCl (solid) (solid) and DOP (liquid oil) aerosols (and DOP (liquid oil) aerosols (0.3 0.3 µµmm) ) charge neutralized at 85 L/mincharge neutralized at 85 L/min3 levels of filter efficiency3 levels of filter efficiency–– 95 = at least 95% efficiency95 = at least 95% efficiency–– 99 = at least 99% efficiency99 = at least 99% efficiency–– 100 = at least 99.97% efficiency100 = at least 99.97% efficiency

3 categories of oil resistance (N, P, R)3 categories of oil resistance (N, P, R)9 classes of respirators9 classes of respirators

NIOSH Tests are NIOSH Tests are ““Worst Worst CaseCase””

Most penetrating particle sizeMost penetrating particle size–– Particles larger Particles larger andand smaller than 0.3 smaller than 0.3 µµm will be m will be

collected with HIGHER efficiencycollected with HIGHER efficiency

Charge neutralized aerosols collected with Charge neutralized aerosols collected with lower efficiency than nonlower efficiency than non--neutralized neutralized aerosolsaerosolsHigh flow rate (85 L/min)High flow rate (85 L/min)PrePre--conditioning at 85conditioning at 85±±5% RH 5% RH and 38and 38±±2.5 2.5 C for 25C for 25±±1 hr1 hr

Evaluation of FitEvaluation of Fit

Health care masks:Health care masks:–– Not part of FDA approval or ASTM filter Not part of FDA approval or ASTM filter

testing methodstesting methodsRespirators:Respirators:–– OSHA Respiratory Protection Standard OSHA Respiratory Protection Standard

(32 CFR 1910.134)(32 CFR 1910.134)–– QLFT and QNFT methodsQLFT and QNFT methods–– Protection factor of 10 for filtering Protection factor of 10 for filtering

facepiece respiratorsfacepiece respirators

Study GoalStudy Goal

Measure filter efficiency and Measure filter efficiency and facial fit for representative facial fit for representative health care maskshealth care masks

MethodsMethods

Nine health care masks used in Nine health care masks used in hospital and dental settingshospital and dental settingsRange of uses (surgical, laser, Range of uses (surgical, laser, procedure)procedure)Range of mask types (cup, flat, Range of mask types (cup, flat, duckbill)duckbill)Range of fastenings (1 or 2 ties, ear Range of fastenings (1 or 2 ties, ear loops)loops)

Filter Efficiency MethodsFilter Efficiency Methods

Three sizes monodisperse latex spheres Three sizes monodisperse latex spheres (0.895, 2 and 3.1 (0.895, 2 and 3.1 µµm)m)6 L/min6 L/minNeutralized aerosolNeutralized aerosolMasks sealed to metal plateMasks sealed to metal plateUpstream and downstream concentrations Upstream and downstream concentrations measured with laser photometermeasured with laser photometer3 replicates of each mask3 replicates of each maskAlso tested 3 replicates of each mask using Also tested 3 replicates of each mask using NIOSH test conditions (84 L/min, 0.3 NIOSH test conditions (84 L/min, 0.3 µµm m NaClNaCl) with TSI Automated Filter Tester) with TSI Automated Filter Tester

Facial Fit MethodsFacial Fit Methods

Only masks with less than 0.6% filter Only masks with less than 0.6% filter penetrationpenetration20 subjects (10 male, 10 female)20 subjects (10 male, 10 female)Medical screening; informed consentMedical screening; informed consentEach subject wore 1 mask, 4 testsEach subject wore 1 mask, 4 tests–– 2 QLFT (2 QLFT (BitrexBitrex) assisted, unassisted) assisted, unassisted–– 2 QNFT (2 QNFT (PortacountPortacount) assisted, unassisted) assisted, unassisted

Health Care MasksHealth Care Masks

AA Medical, cone, one strapMedical, cone, one strap (Not reported)(Not reported)BB Medical, 3Medical, 3--ply, ear loops ply, ear loops (BFE 95%)(BFE 95%)CC Medical, 3Medical, 3--ply, 2 ties ply, 2 ties (BFE 95%)(BFE 95%)DD Procedure, fluid resistant, splashguard visor, pleated, Procedure, fluid resistant, splashguard visor, pleated,

ear loops ear loops (99%, 99%)(99%, 99%)EE Surgical, 3Surgical, 3--ply, pleated, 2 ties ply, pleated, 2 ties (96%, 97%)(96%, 97%)FF Surgical, pleated, 2 ties Surgical, pleated, 2 ties (96%, 97%)(96%, 97%)GG SubSub--micron, fluid resistant, splashguard visor, micron, fluid resistant, splashguard visor,

pleated, 2 ties pleated, 2 ties (99%, 99%)(99%, 99%)HH SubSub--micron, pleated, 2 ties micron, pleated, 2 ties (99%, 99%)(99%, 99%)II SubSub--micron, duckbill, 2 ties micron, duckbill, 2 ties (99%, 97%)(99%, 97%)

Dental MasksDental Masks

020406080

100

0.895 2 3.1Particle Size (um)

Pene

trat

ion

(%)

ABC

Hospital MasksHospital Masks

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0.895 2 3.1

Challenge Particle Size (um)

Pene

trat

ion

% FHDIGE

NIOSH Test NIOSH Test –– Dental MasksDental Masks

020406080

100

A B C

Mask

Pene

trat

ion

(%)

NIOSH Test NIOSH Test –– Hospital MasksHospital Masks

01020304050

F H D I G E

Mask

Pene

trat

ion

(%)

Fit TestsFit Tests

Included only the 5 hospital masks (D, Included only the 5 hospital masks (D, F, G, H and I) with less than 0.6% F, G, H and I) with less than 0.6% penetration for all three test particle penetration for all three test particle sizessizes

Qualitative Fit Test Qualitative Fit Test ResultsResults

All subjects failed the All subjects failed the BitrexBitrex aerosol aerosol qualitative fit test on the first exercise qualitative fit test on the first exercise when donning without assistancewhen donning without assistanceOnly 2 male subjects passed QLFT Only 2 male subjects passed QLFT with assistancewith assistance–– 60% failed on first exercise60% failed on first exercise

Quantitative Fit Test Quantitative Fit Test ResultsResults

Fit factor = 2.5 Fit factor = 2.5 –– 6.9 for unassisted 6.9 for unassisted donningdonningFit factor = 2.8 Fit factor = 2.8 –– 9.6 for assisted 9.6 for assisted donningdonningAverage fit factor for all masks, Average fit factor for all masks, unassisted donning = 4.4 unassisted donning = 4.4 ±± 0.90.9Average fit factor for all masks, Average fit factor for all masks, assisted donning = 5.7 assisted donning = 5.7 ±± 0.8 0.8

Quantitative Fit Test Quantitative Fit Test ResultsResults

Some masks showed improvement Some masks showed improvement after assisted donning, others did notafter assisted donning, others did notGender had no effect on fit factor with Gender had no effect on fit factor with either donning protocoleither donning protocol

ConclusionsConclusions

Health care mask filters exhibit wide range Health care mask filters exhibit wide range of filter efficiencyof filter efficiencyFilter efficiency is not predictive of fit Filter efficiency is not predictive of fit –– Mask with one of the best filter efficiencies had Mask with one of the best filter efficiencies had

lowest fit factorlowest fit factor

BFE and PFE results are not predictive of BFE and PFE results are not predictive of filter performancefilter performanceHealth care masks do not fit and do not Health care masks do not fit and do not meet even minimum expectations for meet even minimum expectations for respiratory protectionrespiratory protection