The SR 540 EX face shield together with the SR 500 EX fan has been approved for use in an explosive atmosphere. The breathing hose of the face shield is connected to the fan equipped with filters. The pressure generated inside the face shield prevents particles and other impurities from being admitted. The SR 540 EX face shield may also be used together with compressed air attachment SR 507 but in this case only in environments which are not potentially explosive. This combination forms a breathing apparatus designed for continuous air flow, for connection to a compressed air supply. See separate product leaflet SR 507. The equipment can be used as an alternative to filter protections in all situations in which the latter are recommended. This applies particularly to situations in which the work is intensive, hot or of long duration.