A respiratory protective equipment is meant to protect a person against hazardous substances present in the atmosphere, where he/she should work under forms like solid or liquid aerosols or gas, vapors or steam.

The user of a respiratory protective equipment must know the nature present risks (composition and concentration of the toxic substances) in the atmosphere in which he/she should work on one hand, on the other hand it’s important to take into consideration the time during which the protection must be ensured as well as the physiologic charge (breathing rhythm) of the user, in order to select a respirator device having the adapted autonomy.