There are a huge variety of filters and cartridges available for half mask and full face respirators. On top of that, OSHA requires that employers choose correctly amongst all this variety. In their words, employers must choose a filtration media that is "appropriate for the chemical state and physical form of the contaminant" present.
What Does This Mean?
This means that the respirator filters or cartridges in use be designed to protect workers from the specific dust, fiber, fume, mist, vapor, or gas hazard present. In other words, the respiratory filtration media should be suitable for the hazard or hazards present.
What Is a Dust, Fiber, Fume, Mist, Vapor or Gas Contaminant?
Dust and Fibers: These are "are solid particles that are formed or generated from solid materials through mechanical processes such as crushing, grinding, drilling, abrading or blasting. Examples are lead, silica, and asbestos."
Fumes: These are "are solid particles that are formed when a metal or other solid vaporizes and the molecules condense (or solidify) in cool air. Examples are metal fumes from smelting or welding. Fumes also may be formed from processes such as plastic injection or extrusion molding."
Mists: These are "are tiny droplets of liquid suspended in the air. Examples are oil mist produced from lubricants used in metal cutting operations, acid mists from electroplating, and paint spray mist from spraying operations."
Gases: These are "materials that exist as individual molecules in the air at room temperature. Examples are welding gases, such as acetylene and nitrogen, and carbon monoxide produced from internal combustion engines."
Vapors: These are "the gaseous form of substances that are normally in the solid or liquid state at room temperature and pressure. They are formed by evaporation. Most solvents produce vapors. Examples include toluene and methylene chloride.
How Do I Choose?
As long as the amount of the above hazards is below the threshold outlined by NIOSH (see your safety data sheet), respirator manufacturers have made it easier than ever to choose the correct filtration media.
If your hazard is a dust, fiber, fume, or mist, the P100 filter should be your go to filter. The universal color for the P100 filter is purple. The P100 filters provide protection from lead and asbestos particles, welding fumes and mists, fiberglass dust, and assorted other dusts, fibers, fumes, or mists.
If your hazard is a gas or vapor, the multi-gas charcoal cartridge will almost always provide you the proper protection. There are some exceptions, of course. These multi-gas cartridges provide protection from organic vapors, chlorine, ammonia, hydrogen chloride, hydrogen sulfide, hydrogen fluoride, and many more gases or vapors. We can help you with a complete list if needed.
If your hazard contains both of the above, then you'd simply require a double-stacked or combination filter cartridge. This cartridge is manufactured with a P100 filter attached to a multi-gas charcoal cartridge. This is typically the most expensive of the three filter cartridges. In some cases, it is possible to attach a P100 filter to a multi-gas cartridge and save money. We'd be glad to assist you with that.