The Occupational Safety and Health Administration, OSHA, states that air-purifying respirators “have filters, cartridges, or canisters that remove contaminants from the air by passing ambient (surrounding) air through the air-purifying element before it reaches the user.” Most have negative pressure; the user pulls air through the filter when he or she inhales. Air-purifying respirators (APRs) have particulate filters, chemical cartridges, canisters, or a combination of these. The powered air-purifying respirator (PAPR) has positive pressure where air is filtered and supplied via a battery-operated blower. APRs are discussed in more detail in the sub-pages that follow.
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| Air-purifying Respirators. Illustration by Donald Barry, University of Maine. |