Particulate respirators are the simplest, least expensive, and least protective of the respirator types available. These respirators only protect against particles. They do not protect against chemicals, gases, or vapors, and are intended only for low hazard levels.
Gas masks are also known as “air-purifying respirators” because they filter or clean chemical gases and possibly particles out of the air as you breathe. This respirator includes a facepiece or mask, and a filter/cartridge (if the filter is in a metal shell it is called a “canister”).
Powered air-purifying respirators use a fan to blow air through the filter to the user. They are easier to breathe through and they need a fully charged battery to work properly.
Self-Contained Breathing Apparatus (SCBA) is the respirator commonly used by firefighters. These use their own air tank to supply clean air, so you don’t need to worry about filters. They also protect against higher concentrations of dangerous chemicals. However, they are very heavy (30 pounds or more), and require very special training to use and to maintain them.