Dust Mask Usage

[K P Steinmeyer <kpstein@gyral.com>]

Richard Rodenbough posted some information that I'd like to add some
comments to.

1.  The new term, wich the NRC is considering adopting, is Assigned
Protection Factor.  This indicates that it is not a measured value but a
more or less arbitrarily assigned number.

2.  NRC is considering NOT requiring that the APF of a respirator be equal
to or greater than the multiple of DAC to which the worker might be
exposed.  NRC is considering basing respirator assignment on ALARA.
Therefore it is possible that in a high radiation area with airborne
contamination that a filtering facepiece might be the best option, even
though the airborne concentration is much greater than 10 times the DAC.
This personally makes sense to me.  If I can enter such an area with NO
respirator and limit dose based on stay, why not use a dust mask too limit
inhalation (ALARA), control dose based on air sample data, and possibly
adjust the assigned dose post exposure using bioassay data?

3.  Current practice in NRC programs is to require a fit factor at least 10
times the APF, not "similar to the PF's" as Mr. Rodenbough suggested.  NRC
is considering maintaining this requirement for negative-pressure devices.  

4.  I strongly agree with Mr. Rodenbough that fit factors are not an
accurate measure of anything.  Some arbitrary fit factor is established as
a minimum qualifier, indicating that a respirator user is able to achieve a
satisfactory face fit with a given size and style of respirator.  Fit
factors DO NOT equal assigned protection factors and cannot be used as
such.  The APFs are set down by NRC (for nuclear programs).

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