Respiratory Protection Terms and Definitions

Air-purifying respirator: A respirator with an air-purifying filter, cartridge, or canister that removes contaminants from the air.

Atmosphere-supplying respirator: A respirator that gives the user breathable air from another source, such as a tank, rather than from the ambient atmosphere. This category includes supplied-air respirators (SARs) and self-contained breathing apparatus (SCBA) devices.

Canister or cartridge: A container with a filter, sorbent, or catalyst (or combination of these) that removes specific contaminants from the air as it passes through the container.

Emergency situation: Any event where equipment fails, such as a container rupture, which results in a release of an airborne contaminant.

Employee exposure: Exposure to a dangerous level of an airborne contaminant.

Engineering controls: Changing the workspace in order to reduce injury or harm to employees. These are typically more drastic changes that are made after work controls are implemented.

Filter or air purifying element: A component in respirators to remove solid or liquid aerosols from the air employees will breathe.

Filtering facepiece (dust mask): A particulate respirator with a filter as an integral part of the facepiece. The entire facepiece may also be composed of the filtering medium.

Fit: The proper use of a respirator so that it covers the areas the respirator is designed to cover. The definition of "fit" will be different for each respirator; for example, loose-fitting respirators do not require a seal to be considered "fit," while tight-fitting respirators do.

Fit test: Qualitative or quantitative evaluations to test the fit of a respirator that a worker is wearing.

Immediately dangerous to life or health (IDLH): An atmosphere that poses an immediate threat to life, could cause permanent health defects, or would impede an individual from safely escaping a dangerous environment.

Loose-fitting facepiece: A respiratory protective device that creates a partial seal with the wearer's face.

Maximum use concentration (MUC): The maximum concentration of a hazardous substance in the atmosphere that an employee can be protected from while wearing a respirator. This measurement is determined by several factors, including the type of respirator and the exposure limit of the hazardous substance in the environment.

Negative pressure respirator (tight fitting): A respirator where the air pressure inside the facepiece is negative (while the user inhales) in comparison to the ambient air pressure outside of the respirator.

Oxygen-deficient atmosphere: An atmosphere with an oxygen content at or below 19.5% by volume.

Physician or other licensed healthcare professional (PLHCP): An individual legally allowed (through a license, registration, or certification) to independently provide the healthcare services covered in this course.

Qualitative fit test (QLFT): A pass/fail fit test that determines if a respiratory device is functioning properly. It uses a test agent, such as an odorous but harmless agent, while the employee wears the device and confirms if he or she can detect the agent.

Quantitative fit test (QNFT): A pass/fail fit test that determines if a respiratory device is functioning properly. It uses a device to numerically measure any respirator leakage.

Self-contained breathing apparatus (SCBA): An atmosphere-supplying respirator for which the breathing air source is designed to be carried by the user.

Service life: The amount of time a respirator or other respiratory equipment will give its wearer proper protection.

Supplied-air respirator (SAR) or airline respirator: An atmosphere-supplying respirator with a breathing air source not carried by the user.

Tight-fitting facepiece: A respiratory device that creates a complete seal with the user's face.

Work practices or controls: Ways of changing the worksite in order to reduce potential injuries and harm to employees. This involves participation from employees and management to identify potential harms and then brainstorm ways to reduce these hazards. The next step after work practices is engineering controls.

To learn more about Respiratory Protection visit our Respiratory Protection Online Training web page.