An approved device which has met the requirements of 42 CFR part 84, has been designed to protect the wearer from inhalation of harmful atmospheres, and has been approved by the National Institute for Occupational Safety and Health (NIOSH) and the Mine Safety and Health Administration (MSHA). Note: 42 CFR part 84 supercedes/ replaces 30 CFR part 11, effective July 10, 1995. The change dealt primarily with particulate respirators. See: Http: //www.cdc.gov/niosh/pt84abs2.html for details. Additional Info: : There are many different kinds of respirators used to prevent or reduce inhalation of hazardous or toxic materials. These fall into two general classes: (1) Atmosphere-supplying respirators. These respirators provide breathingair from a source independent of the surrounding atmosphere. Three types of atmosphere-supplying respirators are: Air-line respirators (also called an air-supplied respirator or supplied air respirator, SAR). The respirator is connected to a stationary source of compressed breathing air source by a hose. The air is delivered continuously or intermittently in a sufficient volume to meet the wearer's breathing requirements. Obviously, the user is restricted by the length of the hose connection, and the dangers of damage to the hose. Also see: This OSHA article, Deaths Involving the Inadvertent Connection of Air-line Respirators to Inert Gas Supplies. Self-contained breathing apparatus (SCBA). This is much like the apparatus a SCUBA diver or fire fighter might use. Air is supplied from a compressed cylinder, usually through a full-face mask, which is worn on the back. This gives greater movement than an air-line respirator, but the air supply is limited. Combination respirators have a small, auxiliary self-contained air supply that can be used if the primary supply fails. (2) Air-purifying respirators. These contain an air-purifying filter, cartridge, or canister that removes specific air contaminants by passing ambient air through the air-purifying element. These do not supply oxygen and mustonly be used when there is sufficient oxygen to sustain life and the air contaminant level is below the concentration limits of the device. In addition, these cartridges/canisters usually do not include any method of indicating when their ability to remove air contaminants has been reduced. Read the manufacturer's instructions for cartridge maintenance and replacement or See: The OSHA link below. There are three basic kinds of air-purifying respirator: Particulate respirators use a mechanical filter to remove particulate matter such as dusts. Do not assume that your respirator removes particulates or vapors; READ the labels and manufacturer's instructions. NIOSH strongly recommends that any particulate devices approved under 30 CFR part 11 be replaced by those approved under 42 CFR part 84. Gas and vapor respirators (or chemical cartridge respirators) use chemicals such as activated charcoalto remove specific gases and vapors from the air. These are effective for concentrations of no more than ten times the TLV of the contaminant, if the contaminant has warning properties (odor or irritation) below the TLV. Combination respirators have filters for both particulates and vapors. Powered air-purifying respirators (PAPR) (not shown) use a blower to force the ambient air through air-purifying elements to the inlet covering. Some other respirator terms worth knowing are: (a) Demand respirators are atmosphere-supplying respirators that admit breathing air to the face piece only when a negative pressure is created inside the face piece by inhalation. This is the same mechanism used in SCUBA (diving) gear. (b) Negative pressure respirators (tight fitting) have negative (lower) air pressure inside the face piece with respect to the ambient air pressure outside the respirator during inhalation. (c) Positive pressure respirators have a pressure inside the respiratory inlet that exceeds the ambient air pressure outside the respirator. (d) Pressure demand respirators are positive pressure atmosphere-supplying respirators that admit breathing air to the face piece when the positive pressure is reduced inside the face piece by inhalation. (e) Escape-only respirators are intended to be used only for emergency exit. (f) High efficiency particulate air (HEPA) filters are at least 99.97% efficient in removing monodisperse particles of 0.3 micrometers in diameter. The equivalent NIOSH particulate filters specified in 42 CFR 84 are the N100, R100, and P100 filters. See also: Asthma, Emphysema, Fume Hood, Respiratory