This British Standard specifies requirements for compressed air line breathing apparatus with positive pressure demand valve for use with a full face mask as a respiratory protective device intended to be used during firefighting, rescue, evacuation, escape, hazard containment and decontamination, and similar activities by emergency first responders (e.g. fire, ambulance, police, and associated civilian agencies and workers) in areas containing and contaminated by chemical, biological, radiological and nuclear (CBRN) agents.