Respirator

Respirators fall into two broad families. Air-purifying types, such as half-mask and full-facepiece models, pull room air through filters for particles or cartridges for gases and vapors. Supplied-air types, including SCBA, bring breathable air from a tank or line and are used where the air is too contaminated, or lacks oxygen, for filtering to work.

In the United States, workplace respirator use is governed by the OSHA respirator rule, 29 CFR 1910.134. It requires a written program, medical evaluation, training, a Respirator fit test for tight-fitting facepieces, and proper maintenance and storage. Respirators used in workplaces are expected to carry NIOSH approval (respirators), and each type has an Assigned protection factor (APF) showing how much protection it can offer when used in a full program.

Choosing a respirator depends on what is in the air, how much, and for how long. The SDS and exposure limits such as the Permissible exposure limit (PEL) help estimate the hazard, but cartridges must match the contaminant. A cartridge for organic vapors does not protect against all gases, and some chemicals have poor warning properties, so smelling the chemical is not a safe indicator that a cartridge still works.

Respirators are normally used when Engineering controls such as Local exhaust ventilation (LEV) cannot keep exposure low enough, during maintenance, or in emergencies. They add physical strain, and facial hair or glasses can break the seal.