The EN 12941 standard specifies minimum requirements for powered filtering devices incorporating a helmet or a hood with gas, particle or combined filter(s) for respiratory protection. It does not cover devices designed for use in circumstances where there is or might be an oxygen deficiency (oxygen less than 17% by volume). Also, it does not cover respiratory protective devices designed for escape purposes.
Specifically, assisted ventilation filtering devices can be full-face masks or half-face masks that protect against specific gases or vapours, particles (solid and/or liquid aerosol) or gas and dust combinations. The filtering device can supply a continuous air feed or depend on breathing. Classified as TM1, TM2 and TM3, they normally consist of:
- a full-face mask, a half-face mask or a facepiece,
- a power turbo unit that supplies the respirator with filtered ambient air,
- one or more filters which all of the air supplied to the mask passes through,
- exhalation valves or other outlets, depending on the structure, through which the breath and the air not needed by the user is discharged.
