Air-Raid Vault Uses Chain of Gas Masks (Aug, 1939) Air-Raid
Vault Uses Chain of Gas Masks Like smokers grouped around a
Turkish bubble pipe, users of a new French air-raid shelter
inhale from a common source. Tubes connect their masks with a
single pipe leading from a battery of oxygen cylinders, as shown
above. Thus they are constantly assured of pure air to breathe,
without recourse to poison-absorbing canisters that hinder free
respiration; and elaborate gasproofing precautions may be
dispensed with.