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the following geometric mean NaCl leakages: 38% through a Willson DM filter, 31% leakage through an MSA DM filter, 28% through a Willson DM filter with acid-gas sorbent, 26% through a Willson DM filter with organic vapor sorbent, 24% leakage through an MSA DM filter with organic vapor sorbent, 23% leakage through an MSA DM filter with acid-gas sorbent, 4.3% leakage through a Willson DFM filter,
and 1.5% leakage through an MSA DFM filter.[1]
In the early 1980s, the following consensus statements were made to NIOSH by respirator experts on the Ad Hoc Air-Purifying Committee of the ANSI Z88 Committee. These experts included several representatives from major respirator manufacturers.
The second shortcoming of the (30 CFR Part 11] certification tests is that the actual aerosols
used could not be related to those found in the workplace nor could they be considered as an aerogo] having the greatest ability to penetrate the respirator filter media of those aerosols likely to found in the workplace. Many alternatives were discussed. The one most feasible aeroso) evaluated was the extremely small (“worst case”) sodium chloride aerosol having a particle size of approximately .12 (geometric count mean) microns in diameter and geometric SD [standard devi- ation] of leas than 1.6... .
The committee decided that in addition to the sodium chloride solid aerosol, the incorporation
(sie) liquid aerosol should be also included to measure the respirator’s efficiency in removing
mists, should that certification be requested. The thermally generated approximately 3 micron , DOP aerosol was chosen as the candidate for respirator certification for mists.
Mists or liquid aerosols will affect filter media in a much different manner than a solid aerosol. With some filter media the liquid particles can have an extremely determental (sic) effect. For example, the committee has generated data that show an “[NIOSH-] approved” mist filter that can be less than 50% efficient when challenged with oil mist. ‘ies
However to summarize, the data the committee obtained indicated that, in many cases, the effi- ciency of the respirator throughout the test when continuously measured was far less than indi- cated by the current (30 CFR Part 11] certification tests. The net result being that should the respirator wearer rely on a respirator currently certified for protection of certain particulates, he or ahe may not receive adequate protection if the environment contains a significant quantity of the “worst case” or hardest to filter contaminants. The committee recommended that NIOSH adopt a proposed alternatives (sic) attached to this report.
The recommended particulate certification would consist of certifying the respirator for protection against either a liquid or a solid aerosol or both in filter efficiency classes of less than 5% [leak- age], less than 1% or less than 0.03% [leakage}.. . ./5
‘Wilmes, D.: Recommendations to NIOSH for Revision of 30 CFR Part 11, memorandum from
chairman of the Ad Hoc Air-Purifying Committee of the ANSI 288 Committee for Respiratory Protec:
tion, St. Paul, MN (undated, ca. early 1980s), p. 2.
- ↑ Ibid., Table VIII, p. 1036.