A respirator is a specialized piece of personal protective equipment (PPE) designed to protect the user from inhaling hazardous atmospheres, such as dusts, fumes, mists, gases, and vapors. These devices work by either filtering contaminants from the surrounding air or by supplying clean, breathable air from an independent source. Selection and proper use are determined by the specific contaminants, their concentration, and the overall environment. Effective respiratory protection relies on a comprehensive program that includes training and proper fit to ensure a sealed barrier against airborne threats.
Categorizing Respirators by Function
Respirators are broadly classified into two categories based on their source of breathable air: Air-Purifying Respirators (APRs) and Atmosphere-Supplying Respirators (ASRs). This distinction dictates the level of protection and the environments where they can be safely used. APRs function by cleaning the ambient air before inhalation. They are appropriate only where contaminant concentration is known, below safety limits, and where sufficient oxygen is present. Conversely, ASRs provide air from an external source, independent of the surrounding atmosphere. ASRs are mandatory for environments considered Immediately Dangerous to Life or Health (IDLH), including atmospheres with high contaminant concentrations or those deficient in oxygen.
Understanding Air Purifying Respirators
Air-Purifying Respirators operate by drawing contaminated air through a filter, cartridge, or canister, which removes hazards before inhalation. The removal mechanism depends on the hazard, utilizing filtration for particles or adsorption/absorption for gases and vapors. Filtering Facepiece Respirators (FFRs), such as the N95, capture airborne particulates using a dense network of fibers. FFRs are rated by efficiency and resistance to oil, designated by a three-part system: N, R, or P, and a percentage (95, 99, or 100).
The rating system indicates:
- N-series: Not resistant to oil.
- R-series: Somewhat resistant to oil.
- P-series: Strongly oil-proof.
The number indicates the minimum percentage of particles removed during testing. Elastomeric respirators use replaceable cartridges or canisters containing sorbent materials, such as activated carbon, which trap gases and vapors. These devices must only be used in atmospheres containing at least 19.5% oxygen, as they clean the existing air but do not supply oxygen.
Supplied Air Systems
Atmosphere-Supplying Respirators provide the highest level of protection because the breathing air source is completely independent of the workplace environment. These systems are required for entry into environments that are oxygen-deficient or contain extremely high, unknown, or immediately hazardous concentrations of contaminants. There are two main designs: Self-Contained Breathing Apparatus (SCBA) and Airline Respirators.
Self-Contained Breathing Apparatus (SCBA)
SCBA consists of a pressurized cylinder of air worn by the user, offering complete mobility for emergency entry or rescue operations. The air supply is limited by the cylinder size, typically lasting 30 to 75 minutes.
Airline Respirators
Airline or Supplied-Air Respirators (SARs) deliver clean air from a remote source, such as a compressor or cylinder bank, through a long hose connected to the facepiece. This tethered system is ideal for prolonged work periods where mobility is less of a concern, as it offers a continuous supply of air.
Achieving a Proper Fit and Seal
The effectiveness of any tight-fitting respirator hinges on achieving and maintaining a perfect seal between the facepiece and the wearer’s face. Without this seal, contaminants can leak into the facepiece, bypassing the filter or air supply and offering minimal protection. Regulatory standards, such as those from the Occupational Safety and Health Administration (OSHA), mandate that personnel required to wear tight-fitting respirators must pass a fit test.
Fit testing is performed before initial use and annually thereafter. It ensures the chosen make, model, style, and size of the respirator matches the user’s facial structure.
Types of Fit Testing
Qualitative Fit Testing (QLFT) is a subjective, pass/fail method that relies on the wearer’s ability to detect a test agent, such as a bitter or sweet aerosol, while wearing the respirator under a hood. Quantitative Fit Testing (QNFT) is an objective method that uses specialized equipment to numerically measure the amount of inward leakage, providing a precise “fit factor.”
Every time a tight-fitting respirator is donned, the user must perform a User Seal Check, a quick procedure to confirm the seal is intact. Factors like facial hair, deep scars, or certain jewelry can interfere with the face-to-facepiece seal, compromising the respirator’s protective function.