A self-contained breathing apparatus (SCBA) is a device worn to provide breathable air in environments with oxygen deficiency, smoke, dangerous gases, and other airborne contaminants that may be otherwise dangerous to breathe. Workers handling hazardous materials or operating in contaminated zones are typically required to wear a self-contained breathing apparatus. Only positive-pressure SCBAs are recommended for entry into atmospheres that are immediately dangerous to life and health (IDLH).