Atmosphere-supplying respirator: A respirator that supplies the user with breathing air from a
source independent of the ambient atmosphere, including supplied-air respirators (SARs) and self contained breathing apparatus units. Supplied-air respirator: An atmosphere-supplying respirator for which the independent source
of breathing air is not designed to be carried by the user. This includes continuous-flow and pressure-demand systems. It’s also known as an airline respirator. Powered air-purifying respirator: An air-purifying respirator that uses a blower to force ambient air through air-purifying elements to the respiratory inlet covering. Positive-pressure respirator: A respirator in which the pressure inside the respiratory inlet covering normally exceeds the ambient air pressure outside the respirator. This includes continuous flow and pressure-demand SARs and powered-air purifying respirators. Negative-pressure respirator (tight-fitting): A respirator in which the air pressure inside the
face piece is negative during inhalation, compared with the ambient air outside the respirator. Helmet: A rigid respiratory inlet covering that also provides head protection against impact and
penetration. Hood: A respiratory inlet covering that covers the head and neck, and may also cover portions of
the shoulders and torso. Loose-fitting face piece: A respiratory inlet covering that is designed to form a partial seal with
the face. Tight-fitting face piece: A respiratory inlet covering that forms a complete seal with the face.