Air-purifying respirators (APRs) work by cleaning the air you breathe using specialized components that remove harmful substances.
Specifically, air-purifying respirators (APRs) work by removing gases, vapors, aerosols (droplets and solid particles), or a combination of contaminants from the air through the use of filters, cartridges, or canisters. Instead of supplying clean air from a separate source, these respirators pull the surrounding air through a purification element before you inhale it.
How the Components Purify Air
APRs utilize different components depending on the type of contaminant they need to filter:
- Filters: These are designed to trap solid particles (like dust, mold spores, or asbestos fibers) and sometimes liquid aerosols (like mist or spray paint). Mechanical filters physically trap particles as air passes through a mesh of fibers.
- Cartridges: These typically contain sorbent materials, such as activated charcoal, which adsorb specific gases or vapors. Cartridges are used to protect against chemical hazards like organic vapors, acid gases, or ammonia. Some cartridges also include a particulate filter layer.
- Canisters: Generally larger than cartridges, canisters also contain sorbent materials for gases and vapors, often in greater quantities, and include particulate filters. They are used for protection against higher concentrations of contaminants or for longer durations.
| Component Type | Primary Contaminants Removed | Mechanism |
|---|---|---|
| Filters | Particles (dust, mist, fumes) | Mechanical trapping |
| Cartridges | Gases and Vapors (chemicals), Particles | Adsorption (gases/vapors), Mechanical trapping |
| Canisters | Gases and Vapors (chemicals), Particles | Adsorption (gases/vapors), Mechanical trapping |
Practical Insights
- Choosing the correct filter, cartridge, or canister is crucial. Using a particulate filter for protection against chemical vapors offers no protection from the vapor hazard.
- The effectiveness of an APR depends on having a proper seal or fit to the wearer's face to prevent contaminated air from leaking around the edges. This is why fit testing is essential.
- Filters and cartridges have a limited lifespan. They must be replaced according to manufacturer guidelines or when you notice increased breathing resistance (for particulate filters) or smell/taste the contaminant (for gas/vapor cartridges).
- APRs should not be used in atmospheres that are immediately dangerous to life or health (IDLH) or in environments with insufficient oxygen, as they only purify existing air, they don't supply oxygen.
Understanding how APRs utilize filters, cartridges, or canisters to remove specific contaminants is key to selecting and using them effectively for respiratory protection.
