ASSIGNED PROTECTION FACTORS AND ISO

PROTECTION LEVELS

Robin Howie

Robin Howie Associates

ISRP, York, April 2013

There are known knowns.These are things we know we know.There are known unknowns.That is to say, these are things we know we don’t know.But there are also unknown unknowns.These are things we don’t know we don’t know.

Donald Rumsfeldt

THE ISO DTS 16973 CLASSIFICATION REGIMEN

Determine max Lab TIL;

Compare max TIL with Table 2 and assign to relevant TIL Level;

Apply the “Safety Factor” relevant to the TIL Level;

Determine the Protection Level (PL) Class.

TABLE 18: Protection level classes

TIL max (%)

Safety Factor

Protection Level

Class

0.001 10 10,000 PL6

0.01 5 2,000 PL5

0.1 4 250 PL4

1 3.3 30 PL3

5 2 10 PL2

20 1.25 4 PL1

OBSERVATION

From personal experience most “high” performance devices give

much lower Lab TIL than the maxima specified in the EN.

So, Lab PF may be higher than the relevant EN NPF for such devices.

OBSERVATION

PL5 is effectively equivalent to current TM3 and full-face –ve

pressure P3.

A more stringent assessment of the data would set the APF for these devices at somewhere around 20.

OBSERVATION

PL5 effectively sets the “NPF” for these devices at 2000 whereas

BS4275 set the APF at 40.

OBSERVATION

The draft ISO classification takes no account of the nature of the device

and therefore fails to address factors that could affect performance in the

workplace, e.g. sweating during heavy work and/or in hot conditions is likely to be more deleterious with ½-mask -ve performance than with

ff-ve or PAPR.

OBSERVATION

Consider the case where YOU may be exposed to, say, 50 fibres/ml of amosite, and you are offered 3 devices fitted with P3 filters,

all meeting ISO PL5:

a ½-mask -ve pressure device; a full-mask -ve pressure device;

and, a full-mask TM3.

QUESTION

How many would choose the

½-mask -ve pressure device?

QUESTION

How many would choose the

full-mask -ve pressure device?

QUESTION

How many would choose the

full-mask TM3?

OBSERVATION

Consider a full-mask PAPR that gave a max TIL of 0.003%: i.e. a Lab PF of 33,000;

The device would be assigned to an ISO TIL class of 0.01%, i.e. a PF of 10,000;

The ISO Safety Factor would be 5, so giving an ISO “NPF” of 2,000.

OBSERVATION

But a known known is that WPF measured for such devices using suitable in-mask sampling probes give 95%iles in the

region of 20-100.

OBSERVATION

The current ISO draft would therefore take us back 20 years to effectively selecting RPE on the basis of NPF.

WPF DATAThere is a fundamental error in how data are presented

for WPF studies that involve continuous in-mask sampling. For the inhale part of the sample duration

in-mask contaminant is collected. For the exhale part only the non-body deposited contaminant is collected. If all of the contaminant deposits in the

body the true WPF is half of the reported WPF. For continuous flow powered or air-fed devices any

exhaled contaminant will be diluted by the incoming air; and the true WPF will be about half

of the reported WPF.

WPF DATA

It would be prudent to half all WPF results from studies with continuous in-mask sampling; including the data from

Howie et al (1996).

WPF DATA

I proposed such correction when drafting of BS4275 but, as such correction would have “rolled down” into setting very low APF for FFR and ½-mask devices, the proposal was

rejected.

WPF DATA

The then available WPF data were evaluated when setting the APF for

BS4275: copies of these data should be available in the BSI archives. If not

available from BSI the relevant references were cited in BS4275.

Further WPF data are now available.

WPF DATA

A major problem, addressed in BS4275, is that most WPF studies carried out in the USA use/used in-mask probes that are

likely to have significantly under-measured in-mask concentrations and therefore caused WPF to be significantly over-

estimated.

POSSIBLE PROBE EFFECTS

PAPR FF-veP3

UK 14-130

Howie et al (1996)

16-50

Tannahill (1991)

US 728

Colton et al (1990)

95

Colton et al (1989)

WPF DATA

WPF derived from US studies must therefore be assessed with care.

A KNOWN KNOWN

“The quantitative fit factors that were obtained did not predict which workers would have the highest or lowest WPF. Although the data were limited, it

appears there was no correlation between WPF and quantitative fit factor.” Colton et al (1989).

8.8.1 “Fitting tests only identify gross misfits and do not guarantee adequacy of fit.” BS4275: 1997

A KNOWN KNOWN

The Zhuang et al (2003) and Han (2002) studies reported correlation between WPF and QnFF.

Zhuang et al studied the correlation over a short period and did not address long-term effects.

Han’s r^2 values for FF <100, the normal “pass” criterion for such devices, was 0.31 and for FF

>100 was 0.02.

A KNOWN KNOWN

The Zhuang et al (2003) and Han (2002) studies reported correlation between WPF

and QnFF. Zhuang et al’s data exhibit declining

correlation as FF increases above 100.

Han’s r^2 values for FF <100, the normal “pass” criterion for such devices, is 0.31

and for FF >100 is 0.02.

ASSUMPTION

Where QnFF are available but Lab PF data are not, it will be assumed that QnFF can used as an indicator of likely

Lab PF.

CALCULATION BASIS

“Required Safety Factors” below will be based on ISO TIL class/95th%ile WPF

AVAILABLE WPF DATA

Howie et al (1996)

4 x TM3 devices

Large diameter deep probe

No Fit Testing for workmen.

All investigators achieved QnFF >10,000

Howie et al (1996)

Work men Invest’r

Device R1 (62) R2 (65) R3 (33) All (177) All (62)

Lab PF >10000 >10000 >10000 >10000 >10000

QnFF na na na na >10000

ISO PF 10000 10000 10000 10000 10000

ISO SF 5 5 5 5 5

ISO PL 2000 2000 2000 2000 2000

95% WPF 40 130 14 40 40

Req’d SF 250 80 670 250 250

AVAILABLE WPF DATA

Riala & Riipinen (1998)6 x PAPR, P3, assumed TM3

Small diameter probe, depth not defined.No Fit testing

-----------------------------------------------------Colton et al (1989), PAPR

Liu probe effectively flush with inner surface of inner cupAll QnFF >1000

Riala & Riipinen, Colton et al (1990)

R&R Colton et al

Device PAPR (31) PAPR (20)

Lab PF >2000 na

QnFF na >1000

ISO PF 1000 1000

ISO SF 4 4

ISO PL 250 250

95% WPF 5 >700

Req’d SF 200 -

AVAILABLE WPF DATA Tannahill (1990, 1991)

3 x Full-mask –ve AP with P3 filtersSampling in visor area

No Fit Testing--------------------------------------------

Colton et al (1989)Full-face –ve

Liu probe effectively flush with inner surface of inner cup

All QnFF >500

Tannahill, Colton et al (1989)

Device A (33) B (28) All (67) _ve

Lab PF >10000 >10000 >10000 na

QnFF na na na >500

ISO PF 10000 10000 1000 100

ISO SF 5 5 5 3.3

ISO PL 2000 2000 2000 30

95% WPF 16 50 20 95

Req’d SF 600 200 500 -

Source Tannahill Colton

AVAILABLE WPF DATA

Myers et al (1984)

2 x loose-fitting AP PHR

Probe on inside surface of vizor opposite mouth

Minimum QnFF >1000

Myers et al (1984)

Device AH3 (22) W-344 (23) Both (45)

Lab PF na na na

QnFF >2000 1200 1200

ISO PF 1000 1000 1000

ISO SF 4 4 4

ISO PL 250 250 250

95% WPF 37 20 30

Req’d SF 30 50 30

AVAILABLE WPF DATA Zhuang et al (2003)

2 x ½masks -ve with P100 filtersProbably shallow Liu probe

ZZ very kindly supplied raw dataStudy deliberately included wearers with

QnFF <100Only data for wearers with QnFF >100

analysed herein

Zhuang et al (2003)

Device 3M 6000

(23)

MSA Comfo ll

(20)

Both

(43)

Lab PF na na na

QnFF >100 >200 >100

ISO PF 100 100 100

ISO SF 3.3 3.3 3.3

ISO PL 30 30 30

95% WPF c20 c50 c50

Req’d SF 5 2 2

AVAILABLE WPF DATA

Myers & Zhuang (1998)

3 x ½ mask DFM, 2 x FFR DM, 8-11 subjects per mask type

Probe probably on inside surface of mask

All QnFF >100.

Myers & Zhuang (1998)

Device Gerson & MSA (20)

All (54)

Lab PF na na

QnFF >100 >100

ISO PF 100 100

ISO SF 3.3 3.3

ISO PL 30 30

95% WPF c20 45

Req’d SF 5 2

AVAILABLE WPF DATA

Hery et al (1993)

2 x FFP2, 3 x ½-mask P2,

1 x ½-mask P3

Flush probe

No Fit Testing

Hery et al (1993)

Device FFP2

(29)

FFP2

(30)

½+P2

(29)

½+P2

(29)

½+P2

(30)

½+P3

(30)Lab PF 37 20 125 17 13 200QnFF na na na na na naISO PF 20 20 100 5 5 100ISO SF 2 2 3.3 1.25 1.25 3.3ISO PL 10 10 30 4 4 3095% WPF 2 2 2 2 2 2Req’d SF 10 10 50 2 2 50

AVAILABLE WPF DATA

Liu et al (2006)

2 x ½ mask OV

Probe on inner surface of mask

QnFF with pass level of 100, FF for 3M device ranged 155-15000

FF for Survivair device ranged

219-76000

Liu et al (2006)

Device 3M SurvivairLab PF na naQnFF 155 212ISO PF 100 100ISO SF 3.3 3.3ISO PL 30 3095% WPF rank 47 9Req’d SF 2 10

AVAILABLE WPF DATAHan (2002)

3 x N95 FFR

Probe probably on inner surface of mask

QnFF 10-200

Han (2002)

Device 3M 8511 MSA FR200 Wilson 10FLLab PF na na naQnFF 20 5 10ISO PF 20 5 5ISO SF 2 1.25 1.25ISO PL 10 4 495% WPF 6 2 3Req’d SF 3 2 2

Summary

The known knowns.

TM3, FF-ve AP

Device TM3 TM3 FF-ve

LabPF/QnFF >10000 >2000 >10000

ISO SF 5 4 5

WPF based SF

80-670 200 200-600

Source Howie ea Riala & Riipinen

Tannahill

PHR, ½-mask, FFR

Device PHR ½

P100

½-veP3

½-veP2 FFP2

LabPF/ QnFF

>1200 >100 200 13-125 20-37

ISO SF 4 3.3 3.3 1.25-3.3

2

WPF based SF

30-50 2-5 50 2-50 10

Source Myers ea

Zhuang

ea

Hery

FFR, ½-mask -ve AP

Device Gerson & MSA

All OV OV N95

LabPF/ QnFF

>100 >100 155 212 >40

ISO SF 3.3 3.3 3.3 3.3 2-3.3

WPF based SF

5 2 2 10 5-10

Source Myers & Zhuang Liu et al Han

Known unknowns

What are the effects of higher then moderate work rates on TIL?

(See TNO data on Gas Masks and consider the sweating of wearers working hard; particularly when wearing impervious clothing.)

CONCLUSION

The current draft ISO classification regimen fails to address the WPF data base and is

therefore highly likely to put RPE wearers at unnecessary, avoidable, and thus negligent, risk: particularly for the

nominally “high” performance AP devices.