This notice is the first update of the NIOSH Guide to the Selection and Use of Particulate Respirators Certified under 42 CFR part 84 (NIOSH No. 96-101) published in January 1996. It modifies the NIOSH service time recommendations for P-series particulate respirators.

The Guide provided that, "Use and reuse of the P-series filters would be subject only to considerations of hygiene, damage, and increased breathing resistance." The Guide also stated that "NIOSH will be conducting and encouraging other researchers to conduct studies to assure that these service time recommendations are adequate. If research indicates the need, additional service time limitations may be recommended by NIOSH for specific workplace conditions."

Recent NIOSH laboratory studies indicate the efficiency of P-series filters may be significantly reduced with long term use in the presence of oil aerosols. Such long term oil exposure has resulted in the reduction in efficiency of P100 filters to efficiencies much less than that required of P95 filters. In some workplace situations, this reduction in filter efficiency may not always be accompanied by an increase in breathing resistance that would signal the user to replace the filter, or filter element. This reduction in filter efficiency varies significantly from model to model and NIOSH can not make a single filter change recommendation that is appropriate for all models. Therefore, NIOSH has requested each manufacturer of P-series filters to establish service time recommendations as part of their user instructions. NIOSH expects that manufacturers of P-series filters will provide such recommendations as part of their customer support programs.

These NIOSH recommendations are interim in that a full understanding of the degrading effects of workplace contaminants on filter efficiency is not yet available to NIOSH. In addition to continuing to study the degrading effects of workplace aerosols on all types of filters certified under 42 CFR part 84, NIOSH is also investigating the possible degrading effects of workplace gases and vapors on those filters.

Respirator users are also reminded that the provisions of the new 42 CFR part 84 require respirators to be far more resistant to filter degradation than did the provisions of 30 CFR part 11. That is only one of the reasons why NIOSH encourages users to discontinue the use of particulate respirators certified under 30 CFR part 11 and switch to the new particulate respirators certified under 42 CFR part 84.

Users are also reminded that NIOSH has a long standing recommendation that all 30 CFR part 11 particulate filters be replaced at least daily (once each work shift).

This User Notice does not change the NIOSH service time recommendations made in the Guide for N- and R- series respirators.

All filters. The service life of all filters is limited by considerations of hygiene, damage, and breathing resistance. All filters should be replaced whenever they are damaged, soiled, or causing noticeably increased breathing resistance.

N-series filters generally should be used and reused subject only to considerations of hygiene, damage, and increased breathing resistance. However, for dirty workplaces that could result in high filter loading (i.e., 200 mg), service time for N-series filters should only be extended beyond 8 hours of use (continuous or intermittent) by performing an evaluation in specific workplace settings that demonstrates: (a) that extended use will not degrade the filter efficiency below the efficiency level specified in Part 84, or (b) that the total mass loading of the filter(s) is less than 200 mg. These determinations would need to be repeated whenever conditions change or modifications are made to processes that could change the type of particulate generated in the user's facility.

R-series filters should be used only for a single shift (or for 8 hours of continuous or intermittent use) when oil is present. However, service time for the R-series filters can be extended using the same two methods described above for N-series filters. These determinations would need to be repeated whenever conditions change or modifications are made to processes that could change the type of particulate generated in the user's facility.

P-series filters should be used and reused in accordance with the manufacturer's time-use limitation recommendations when oil aerosols are present. P-series filters should be used and reused subject only to considerations of hygiene, damage, and increased breathing resistance if oil aerosols are not present.

30 CFR part 11 filters should be replaced at least daily or more often if breathing resistance becomes excessive or if the filter suffers physical damage (tears, holes, etc.) Filter elements designed to be cleaned and reused should be cleaned at least daily in accordance with the manufacturer's instructions. Between uses, filters should be packaged to reduce exposure to conditions which cause filter degradation, such as high humidity.