demand mask

demand mask

An oxygen mask through which oxygen flows only when the wearer inhales. There is no oxygen flow when the wearer is exhaling. Most combat aircraft have demand oxygen systems, and combat crews use demand masks.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved
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The CBI's head of economic analysis, Doug Godden, said the gloomy national picture for manufacturing demand masked significant regional differences.