Breathing masks or helmets, e.g. affording protection against chemical agents or for use at high altitudes {or incorporating a pump or compressor for reducing the inhalation effort having means for creating a fresh air curtain}
Breathing masks or helmets, e.g. affording protection against chemical agents or for use at high altitudes {or incorporating a pump or compressor for reducing the inhalation effort having means for creating a fresh air curtain}