What type of air is utilized in a supplied-air respirator (SAR)?

A supplied-air respirator (SAR) is designed to provide clean, breathable air from a source other than the ambient atmosphere, typically through a hose connected to an air supply. The correct answer identifies the specific quality of the air that must be ensured for safety.

Grade D air is the standard defined by the American National Standards Institute (ANSI) for breathable air used in respirators. This designation indicates that the air must meet certain purity standards, ensuring it is free from contaminants such as carbon monoxide, carbon dioxide, oil, and other hazardous substances. It specifies criteria for moisture content and overall air quality, which are crucial for protecting the health of individuals using the respirators in potentially hazardous environments.

The other types of air mentioned in the choices do not meet the specific quality requirements set for breathing air in the context of SARs. For example, while compressed air can be a source of breathing air, it does not inherently meet the purity standards unless it has been treated to become Grade D air. Filtered air can refer to any air that has undergone some level of filtration, but it does not guarantee compliance with the stringent quality requirements of Grade D air. Grade A air is a term more often used for high-purity gases in industrial applications rather than for