A powered air respirator kit comprising visor (9) removably attachable to a front edge of a safety helmet (4), a drive unit (1) removably attachable to said safety helmet (4), at least one filter module removably attachable to said safety helmet such that, in use, a fluid flow path is defined through said filter module to a space defined between a user's face and an inner surface of said visor, the kit further comprising a power module (10) removably attachable to said safety helmet and, in use, electrically connectable to said drive unit (1).