Definitions List

Air-Purifying Respirator   
A respirator which cleans contaminants from the air via cartridges and/or filters before the air is inspired by the wearer. These are the most commonly used respirators and are available in half-mask, full-face or powered units.

Approved Respirators   
Tested and listed as satisfactory, by the National Institute for Occupational Safety and Health (NIOSH). or jointly, by the Mine Safety and Health Administration (MSHA). 42 CFR 84 adopted in July 1995 gives NIOSH primary responsibility for certifying most respirators.

Canister (Air-Purifying)   
A container filled with sorbents and catalysts that removes gases, vapors, and/or particulates from air drawn through the unit. Canisters rely on a variety of mechanisms for contaminant removal such as chemical absorption, adsorption, catalytic action, neutralization, and mechanical filtration.

A container filled with sorbents and catalysts that removes gases, vapors, and/or particulates from air drawn through the unit. Cartridges are smaller than canisters but are designed to work on the same principles.

Confined Space   
An enclosure such as a storage tank, boiler, sewer, underground utility vault, tunnel or pit that is difficult to enter or exit and may contain atmospheric or physical hazards.

An irritating or potentially harmful material (gas, vapor, or particulate) which is foreign to the normal atmosphere.

Exhalation Valve   
A device that allows exhaled air to leave a respiratory device and prevents outside air from entering through the valve.

The portion of a respirator that covers the wearer's nose and mouth (a full-facepiece also covers the eyes). The facepiece should make a gas-tight or dust-tight seal with the face. The facepiece is supported by headbands, and contains inhalation valves, exhalation valves and connectors for the air-purifying cartridges or filters.

A fibrous medium used in respirators to remove solid or liquid particulates from the air before it enters the facepiece (this term may be used interchangeably with cartridge).

Airborne particulate formed by the evaporation of solid material e.g. metal fume emitted during welding.

High-Efficiency Particulate Air (HEPA) Filter   
A filter designed to remove 99.97% of particulates which are 0.3 microns in diameter. HEPA filters are often referred to as absolute filters and are used to remove toxic respirable sized particles from contaminated air.

IDLH Atmosphere   
An atmosphere Immediately Dangerous to Life or Health. An IDLH atmosphere poses an immediate hazard to life, such as being oxygen deficient (containing less than 19.5% oxygen), or one which produces an irreversible debilitating effect on health.

Inhalation Valve   
A device that allows air to enter the facepiece through the filtering media but prevents exhaled air from leaving the facepiece through the intake openings.

Mine Safety and Health Administration (MSHA)   
Federal Agency that tests, approves and certifies respiratory protection equipment used in mine and mining operations.National Institute for Occupational Safety and Health (NIOSH)    A Federal agency that tests, approves and certifies respiratory protection equipment.

Particulate Matter   
A suspension of fine solid or liquid particles in air, i.e. dust, fog, fume, smoke or sprays. Particulate matter suspended in air is commonly known as an aerosol.

Particulate Filter Series N - P - R   
Effective July 1995 new performance criteria were established for particulate respirators. The new criteria eliminates classification of particulate filters according to hazard such as "dust mist fume" and provides for three levels of filter efficiency (95%, 99%, 99.97%).These efficiencies are available in a series of filter types known as N, R, and P (see the table below). These new respirators will afford a higher level of protection to a variety of workers including hospital employees needing protection from infectious tuberculosis, carpenters, painters, and farmers. NIOSH has established a three year transition period for instituting the new regulation. After July 10, 1998 all particulate respirators will have to be certified under the new criteria.

Efficiency   NaCl Test Aerosol    DOP Test Aerosol(oil resistant)       DOP Test Aerosol(very oil resistant)
95%   N95    R95    P95
99%   N99     R99    P99
 100(99.97%) N100     R100    P100


For the purpose of this manual, the terms "pesticide" and "pesticide chemical" are synonymous with "economic poison", as defined under the United States Department of Agriculture's (USDA) Federal Insecticide, Fungicide and Rodenticide Act (FIFRA).

Protection Factor   
The overall protection afforded by a certain type of respirator as defined by the ratio of the concentration of contaminant outside a face mask or hood to that inside the mask while in a contaminated atmosphere. For example, if a half-mask respirator has a protection factor of 10, it may provide adequate protection in atmospheres where the contaminant concentration is up to 10 times the permissible exposure limit (PEL) for that specific contaminant.

Qualitative Fit Test   
A test procedure to determine the effectiveness of the seal between the face mask and the wearer's face, usually performed during the fitting process.

Quantitative Fit Test   
A scientifically-based test that measures numerically the extent of respirator fit and therefore can be used to assign a protection factor to a specific face-to-facepiece seal.

Opposition to the flow of air, as through a canister, cartridge or particulate filter.

A device designed to protect the wearer from inhalation of harmful atmospheres.

Self-Contained Breathing Apparatus (SCBA)   
A unit designed to provide the wearer with a respirable atmosphere independent of the ambient air. The air supplied by gas cylinder which is carried on the back of the wearer.

Supplied-Air Respirator   
A hose-mask or hood type respirator where respirable air is supplied through an air hose connected to a compressed-air cylinder or air compressor.

The gaseous state of a substance that is a solid or liquid at normal temperature and pressure.