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Re: Appropriate Use of Respirator Protection Factors

Martin, you are correct.  To my knowledge, a 'combination' respirator means
one that can operate in more than one mode - eg. an airline respirator that
converts to a negative pressure respirator if the air supply is lost.
Since these operating modes are independant of one another, the protection
factor is for the particular mode which is used at any given time.  By
definition, the modes defined in the table are different from each other -
i.e. it's either pressure demand, demand, or constant flow - not some
combination of two or more of them at once.  Even if there was such a
beast, at best, all you could do is claim the PF for ONE of those modes.
Multiplying the PF of two or more modes together would be a BIG no-no.

>This question relates to the proper interpretation of 10CFR20, Appendix A,
>specifically, the table of allowed protection factors for respirators.
>Part III of the same table notes that for use of any combination of
>air-purifying and atmosphere-supplying respirators,  the protection factor
>should be the same as for, " - - - type and mode of operation as listed
>above".   My interpretation of this is that only a single protection factor
>for combined use of respirators is allowed.  That is, one may not simply
>multiply the protection factor for each of the respirators to obtain the
>net multiplicative effect.   Consequently, the maximum protection factor
>allowed is 10,000, [SCBA, full facepiece, PD] regardless of how respirators
>are combined.
>Others have the opinion that this is not the case; that in fact, use of two
>different types of respirators in combination permits multiplying
>protection factors of each in order to obtain a net effective protection

Keith Welch
Thomas Jefferson National Accelerator Facility
Newport News VA
Ph: (757)269-7212