Selecting between supplied air and powered air.
Shockley
Brian
B
Bullard, Cynthiana, Ky., USA.
D004867:Equipment Design; D006801:Humans; D016272:Occupational Health; D012134:Respiratory Protective Devices / Q000592:standards; D014481:United States; D014489:United States Occupational Safety and Health Administration / Q000592:standards