oxygen supply 4 hours scba scuba air line respiratory repirator gas mask cartridges high pressure to low pressure oxygen regulator 2216 psi scott dot tested bio hazard environment h2s co flammable xylene petrol gasoline gas fumes cleaning in oil terminals for exploration digging drilling underwater mining excavation ship aircraft safety health and environment she projects laboratories confined spaces etc , no 220 volt is required to charge , self driven , no battery required , equal flow , 30 minutes , one hour 2 hours 3 hours , 4 hours duration