Drager Automatic Switch Over Valve, Occasional fit Breathing Apparatus

Automatic Switch Over Valve - Occasional fit Breathing Apparatus. The Dräger Automatic Switch Over Valve (ASOV) enables the user to connect compressed air breathing apparatus to an external air supply, such as a factory ring main, and be safe in the knowledge that if the external supply were to fail, there would be a safe and uninterrupted transition to the wearer's back-up supply.