The EN 405 standard specifies the use requirements, test methods and marking requirements for filtering facepieces with valves incorporating gas filters or combined filters, used as respiratory protective devices, with the exception of escape appliances. It does not apply to gas or combined facepieces which do not have valves or which are equipped only with exhalation valves. It does not apply to devices intended for use in situations where there is or may be an oxygen insufficiency (oxygen less than 17% by volume). It contains laboratory tests and practical use tests aimed at establishing compliance with the requirements.