Do not use air purifiers to provide protection from the dangers of oxygen-limited environments. Respirators are effective only up to their specified concentration limits. The composition of a respirator's filter depends on the contaminant to be filtered. Various chemicals are used to remove gases and vapors. The useful life of the respirator is determined by the contaminant concentration, breathing volume of the wearer and capacity of the air purifying medium.
Mechanical filters provide protection against particulates such as dusts, mists or metal fumes.
A fibrous material in the filter traps the particles. A mechanical filter respirator with toxic dust approval should be used to protect against grain dusts and mold spores. It should seal tightly around the nose and mouth. A fume-approved respirator of this type also should be worn when welding. Do not use a mechanical filter for protection from chemicals or toxic gases.