Respirator Types: A Brief Guide

• Particulate respirators: These respirators are designed to filter particles, such as dust, mist, and fumes, from the air. Particulate respirators do not protect the user from vapors or gases. Dust masks (sometimes called filtering face piece respirators) are particulate respirators. Particulate respirators carry two primary ratings: A letter rating (N, R, or P) and an efficiency rating. The letter rating refers to how resistant to oil particles the respirator is. If the atmosphere is one where there are no oil particles, either an N, R, or P respirator can used. If there are oil particles present, an R respirator is used for single shift use and a P respirator is used for multiple shift use. The efficiency rating (95, 99, or 100) provides an indication of the filter leakage. The higher the efficiency rating, the less leakage that can be expected. Some regulations (for example, those regarding working with lead) will specify the efficiency rating required for a respirator.
• Gas and vapor respirators: Gas and vapor respirators are used when there are hazardous gases or vapors in the air. These respirators use canisters or cartridges to filter the air. The cartridges that are used with these types of respirators must be matched to the specific contaminant the user will be exposed to. Gas and vapor respirators do not provide protection from particles in the air. 
• Combination respirators: As their name suggests, combination respirators filter both particulates and gases and vapors from the air.
  

• Atmospheres with contaminant for which there are no approved cartridges for air-purifying respirators
• Welding of toxic metals
• Abrasive blasting
• IDLH atmospheres
  

• Supplied-air respirators (SARs) : These supply air to the user through an airline from a source outside the work area. Because there is an airline attached to the unit, one downside of an SAR is that the work range of the individual is limited by the length of the air hose. Another issue with SARs is that airlines can become entangled or pose trip hazards. Generally, SARs are used when there is a requirement for an extended work period in work environments where there is not an IDLH atmosphere.
• Self-contained breathing apparatus (SCBA): SCBAs provide air to the user through a pressurized tank or cylinder carried by the user. SCBAs provide more freedom of movement than SARs. However, because a tank is used, the work time is limited by how long the air supply in the tank lasts. SCBAs are usually the choice for short work periods (generally less than 4 hours) in IDLH atmospheres.
• Combination respirators: Combination respirators are SAR systems that have an auxiliary SCBA that is used in the event of a malfunction of the SAR, allowing safe escape from a hazardous environment. Combination respirators are generally the choice when there is an extended work period required in an IDLH atmosphere.
• Escape-only respirators: These are small SCBA respirators used to exit a hazardous-atmosphere environment in the case of an emergency. Because they are meant to be used for escape situations and carry only a small amount of air, they should not be used to enter an area with a hazardous atmosphere.