Some of the common hazards in the workplace air are dust, gases, fumes, mists and vapors. These can seriously affect the health of workers. Inhalation of these harmful contaminants can lead to crippling lung diseases like lung cancer.

The most important defense against respiratory hazards is to control the contamination at its source and prevent it from entering the air. However, in some situations it may be necessary to wear respiratory protective equipment. This may be because it is not immediately practical to control the contamination. Or it may be because access to contaminated areas is needed for a short period, or maintenance operations need to be carried out. In addition, respiratory protective equipment may need to be worn in some emergency situations.