a John Stenhouse mask from 1870; useful for 'permitting respiration in places where the atmosphere is charged with noxious gases, or vapors, smoke, or other impurities.'
National Institute for Occupational Safety and Health Standard for Filter Selection By Angela Babin, M.S.
In 1995, the National Institute for Occupational Safety and Health (NIOSH) published its revised respirator standards for particulate respirators (see NIOSH Certified Equipment List). These new respirator certification standards were upgraded from those of Part 11 (Title 30 of the Code of Federal Regulations (CFR), Part 11) to those of Part 84 (Title 42 of the Code of Federal Regulations (CFR), Part 84), regarding filters only; the gas/vapor requirements are unchanged.
A comprehensive respirator program must be instituted prior to the use of either Part 11 or Part 84 respirators. The details of a respirator program can be found in the American National Standards Institute (ANSI) Z88.2 (1992), Practices for Respiratory Protection. The legal requirements are found in the Occupational Safety and Health Administration (OSHA) standard 29 CFR 1910.134.
This article outlines the differences between filter selection under the old standard (Part 11) and give some basic guidelines for filter selection under the new standard (Part 84).
Filter selection is relevant to two types of respirator use: 1) a half- or full-face air purifying negative-pressure respirator that can be equipped with both chemical cartridges and/or particulate filters; and 2) re-usable disposable masks (like the 3M 8710 toxic dust mask).
Summary of the Old Part 11 Standard
Filters under the old standard were called: dust and mist (DM), dust, fume and mist (DFM), high efficiency particulate and aerosol, (HEPA), as well as spray paint, and pesticide. The filters on all Part 11 respirators contain certification numbers like TC-21C-xxx or TC-23C-xxx.
Dust, Mist (DM) respirators are labeled as "permissible respirator for dusts and mists or approved for respiratory protection against dust and mists having a time-weighted average (TLV) not less than 0.05 milligram per cubic meter or 2 million particles per cubic foot."
Dust, Fume, and Mist (DFM) respirators are labeled as "permissible respirator for dust, fumes, and mists or approved for respiratory protection against dusts, fumes and mists having a TLV not less than 0.05 milligrams per cubic meter or 2 million particles per cubic foot.
High efficiency respirators (HEPA filter respirators) are labeled as "permissible respirator for dusts, fumes, mists, and radionuclides or approved for respiratory protection against dusts, fumes and mists having a TLV less than 0.05 milligram per cubic meter or 2 million particles per cubic foot and radionuclides." The filter (or in a disposable respirator, the exhalation valve) in a HEPA respirator is usually color coded magenta (reddish-purple).
Paint spray respirators are labeled as "Permissible chemical cartridge respirator for mists of paints, lacquers and enamels or approved for respiratory protection against lacquers and enamels." Pesticide respirators are labeled as "Permissible chemical cartridge respirator for pesticides or approved for respiratory protection against pesticides."
Laboratory test data indicated that some DM and some DFM respirators allow unexpectedly high penetration of particles that are 2 micrometers or smaller in diameter. Therefore, NIOSH recommends (and ANSI requires) that if the contaminant is an aerosol, with a very small size (less than 2 microns) or of unknown particle size, a HEPA filter should be used.
Summary of New Part 84 Standard
The new "Part 84" filters must pass a more demanding certification test than the old filters. The new regulation provides for nine classes of filters (three levels of filter efficiency, each with three categories of resistance to filter efficiency degradation). The three levels of filter efficiency are 95%, 99%, and 99.97%. The three categories of resistance to filter efficiency degradation are labeled N, R, and P. N means not resistant to oil, R resistant to oil, and P oil-proof. These categories are a useful memory key.
(Actually, the "R" is as resistant to oil as the "P," but it has a time-use limitation.)
The class of filter is clearly marked on the filter, filter package, or respirator box. For example, a filter marked N95 would mean an N-series filter that is at least 95% efficient. Chemical cartridges that include particulate filter elements will carry a similar marking that pertains only to the particulate filter element. The filter packaging of Part 84 particulate respirators contain certification numbers of the form TC-84A-xxx.
Respirators certified under Part 11 can be sold and shipped by the manufacturer as NIOSH-certified until July 10, 1998, and can be used after this date, however OSHA has not determined actual filter use past July 1998.
Filter Selection Users can identify three types of filters with three efficiencies each as follows: Respirators with N100, N99, and N95 filters (99.97%, 99%, and 95% efficient filters) may be used for any solid or non-oil containing particulate contaminant. Respirators with R100, R99, and R95 filters (99.97%, 99%, and 95% efficient filters) may be used for any particulate contaminant. If used for an oil containing particulate, a one shift use limit applies. Respirators with P100, P99, and P95 filters (99.97%, 99%, and 95% efficient filters) may be used for any particulate contaminant. No time restrictions apply, the limitations are hygiene and breathing resistance. No particle size limits apply to respirators with Part 84 filters. Protection for the user is based on the efficiency of the filter and the PEL of the contaminant.
Particulate Respirator Selection and Use If you already own a respirator, but want to purchase new filters, the following guidelines will aid in your choice of filter. Using these guidelines may result in filter recommendations that exceed those actually required in a particular work setting. (For example, because both the 99% and 95% filters outperform the DM and DFM filter classes, there may be situations where the 99% or 95% filters are an appropriate substitute for a HEPA filter). See Table 1 for filter recommendations for specific processes.
1. If you are currently using a DFM or DM filter: • In a work setting free of oil aerosols, the minimally protective filter would be an N95. • In a work setting that may contain or does contain oil aerosols, the minimally protective filter would be an R95 or P95.
2. If you are currently using a HEPA filter: • In a work setting free of oil aerosols, an N100 filter would be protective. • In a work setting that contains or may contain oil aerosols, an R100 or P100 filter would be protective. The P100 filter looks exactly like the old HEPA filters - with the magenta colored casing etc.
3. If you are currently using a paint-lacquer-enamel combination cartridge: • In a work setting free of oil aerosols, a combination respirator consisting of an organic vapor cartridge and an N95 particulate filter with an optional prefilter (to prevent rapid clogging by paint aerosols) would be minimally protective. • In a work setting that may contain or does contain oil aerosols, a combination respirator consisting of an organic vapor cartridge and an R95 or P95 particulate filter with a prefilter (to prevent rapid clogging by paint aerosols) would be minimally protective. 4. If you are currently using a pesticide respirator for protection against a particulate and an organic vapor: • A combination respirator consisting of an organic vapor cartridge and an N95 (non-oil aerosols) or an R95 or P95 particulate filter would be minimally protective. • As another example, a particular pesticide may have such low vapor pressure that only a particulate filter may be needed. Thus in certain situations, there may be no need for a combination particulate filter and organic vapor cartridge as recommended above. • If the pesticide contains oil, then an R95 or P95 particulate filter would be the minimal protection.
Remember that particulate filters will not protect against gases or vapors. In the chart below, listed are both the new filter recommendations and the chemical cartridge recommendations. Note that sometimes two filters are listed. This is because some filter types (e.g. N99, N100) may be difficult to find on the current or future market.
Table 1. Filter and Cartridge Selection Chart
Substance of Process CartridgeFilter Aerosol Spray Cans OVN95 Air brush Water based -N95 solvent-basedOVN95AmmoniaAN100, HEPA Asbestos-N100Dusts (Silica): clay, glazes, etc -N95Dye Powders - N95Fiberglass--FormaldehydeFORP95Glycol Fogs (theatrical) --Hydrochloric Acid AGN95 if acid mist generated LacquersOV-Metal grinding with no or water-based lubricant -N95 with lubricant oil -P95Metal melting -N95 Cadmium-N100 Lead- N100Metal Powders - N95Oil Mists (theatrical smoke) - P95Paint strippers (solvent type) OV- Pastel Dusts - N95 (higly toxic metals) -N100Pigment powders -N95 (highly toxic metals) -N100Plastic, resins, and glues OV -Plastics sanding , grinding, etc. -N95 Polyvinyl chloride AGN95 Polyeurathane* (see diisocyanate article re:decomposition) OVN95 Formaldehyde plastics FORN95Silica-N100Soldering (lead) -N100 with acid, fluoride, zinc chloride fluxes AGN100SolventsOV-Spraying water-based-N95 solvent-based OVN95Sulfur dioxide AG-Welding (metal fumes only) -N95 (except lead, highly toxic metals) N100 Key A-ammonia AG-acid gas