RE: dust mask usage -Reply

[RodenboughRC@nswccd.navy.mil]

For a good discussion on Protection Factors and Fit Factors, check out the
NIOSH Respiratory Decision Logic Manual.  Don't know if it's available on
their website.

** Remember that PF is the number assigned to a respiratory protection
device by NIOSH and/or ANSI.  Basically it's a indicator that allows one to
choose an appropriate respirator for the known or expected airborne exposure
concentration to be encountered (hence the reason for doing hazard
assessments that include personnel air sampling).  For example; a full-face
respirator with a protection factor of 100 would only be allowed in a work
environment where the wearer would encounter no more than 100 X the PEL of
the contaminant.

**The FF is the measure of how well a particular facepiece fits the
individual.  As stated, this is usually expressed numerically and can be as
high as 10,000.  But even though the numbers are both based upon the
concentration inside the mask versus outside the mask they are not
interchangeable.   You could get a FF of several hundred for a half-mask
facepiece but the PF is only 10 (depending upon NIOSH/ANSI).  You simply
shouldn't be allowed (nor is it technically correct) to use it in an
environment where the airborne exposure concentration is expected to be
greater than 10X the PEL.

So what does it all mean?  Dust masks (filtering facepieces) don't have PF's
of 200; right now they are at 10.  I doubt that you could get even a high FF
because of sealing problems.  Check your local Respiratory Protection
Program  and with the IH's or HP's that administer it.  IMHO, FF numbers
beyond the assigned PF are essentially meaningless.  The program for
fit-testing should have pass/fail indicators that are similar to the PF's.
High FF's should only be used as an indicator of how well that facepiece
fits to that individual.

Richard C. Rodenbough
Industrial Hygienist
NNMC/IH Dept/BMC-Carderock
9500 MacArthur Blvd
West Bethesda, MD  20817-5700
301-227-5383
F 301-227-4610



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