The Definition of Air-Purifying Respirator (APR)

Definition of Air-Purifying Respirator (APR)

An air-purifying respirator (APR) is a respirator that removes contaminants from the surrounding air by drawing it through filters, cartridges or canisters before the wearer breathes it. APRs include filtering facepieces such as N95s, reusable elastomeric half-mask and full-facepiece respirators, and powered air-purifying respirators (PAPRs) that use a battery-powered blower. Because an APR cleans the existing air rather than supplying fresh air, it cannot be used in oxygen-deficient atmospheres, below 19.5 percent oxygen, or in atmospheres that are immediately dangerous to life or health (IDLH).

Key Facts About Air-Purifying Respirators

• Particulate filters are NIOSH rated N, R or P for oil resistance and 95, 99 or 100 for filter efficiency.
• Gas and vapor cartridges are chemical specific and need a change-out schedule unless they have an end-of-service-life indicator.
• Assigned protection factors: half mask 10, full facepiece 50, loose-fitting PAPR 25, full-facepiece PAPR 1,000.
• Tight-fitting APRs require a medical evaluation and fit testing before first use and at least annually, under 29 CFR 1910.134.

Example of an Air-Purifying Respirator

Painters spraying a solvent-based coating in a ventilated booth wear full-facepiece APRs with organic vapor cartridges and P100 prefilters. Air monitoring confirms vapor levels are within the respirator's protection factor, and cartridges are changed at the end of every shift according to the site's written change schedule.

How to Select an Air-Purifying Respirator

1. Identify the contaminants and measure or estimate their concentrations.
2. Confirm the atmosphere has at least 19.5 percent oxygen and is not IDLH.
3. Choose a respirator whose assigned protection factor keeps exposure below the limit.
4. Select the correct filter or cartridge for each contaminant.
5. Set a cartridge change schedule based on manufacturer data and exposure conditions.
6. Complete medical evaluation, fit testing and training before use.

Related Terms

• Respiratory Protection
• N95 Respirator
• Immediately Dangerous to Life or Health (IDLH)
• Asphyxiant

Frequently Asked Questions: Air-Purifying Respirator

What is the difference between an APR and a supplied-air respirator?

An APR filters the air around the worker, while a supplied-air respirator or self-contained breathing apparatus (SCBA) delivers clean breathing air from a compressor, cylinder or other source. Supplied air is required in oxygen-deficient or IDLH conditions.

Do N95 respirators protect against gases and vapors?

No. N95 filtering facepieces only capture particles such as dust, mist and fumes. Gases and vapors need a respirator fitted with the correct chemical cartridge.

How often should APR cartridges be changed?

Particulate filters are replaced when damaged, soiled or hard to breathe through. Gas and vapor cartridges must follow a written change schedule based on the contaminant, concentration, humidity and work rate, because workers can't rely on smell to tell when a cartridge is spent.