The SR 500 EX fan is explosion-proof and specially adapted for use in an explosive atmosphere. The SR 500 EX is included together with filters and head-tops in Sundström fan-assisted respiratory protective devices. The SR 500 EX 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. The fan is equipped with filters and the filtered air is supplied through a breathing hose to the head-top. The latter is then pressurized, which prevents the surrounding pollutants from being admitted.