Atmosphere-supplying respirators supply clean air directly to the user from a tank or compressor. An atmosphere-supplying respirator has positive pressure, because air is delivered to the breather. The tank may be stationary with an air hose to the respirator (supplied-air respirator), or portable and worn on the user’s back, called a self-contained breathing apparatus or SCBA. SCBA respirators are appropriate for areas considered immediately dangerous to life or health (IDLH). They are used when there is very little oxygen, such as in fire-fighting or in high concentrations of a very toxic pesticide in an enclosed area, such as during a fumigation.
Illustration by Donald Barry, University of Maine.