https://www.afmc.af.mil/News/Photos/igphoto/2001966060/
AF announces corrective measures for oxygen breathing system in training aircraft
The Air Force will begin implementing a series of corrective measures, including redesigning the oxygen system and adjusting oxygen control levels in flight,...
breathing systemafannouncescorrectivemeasures
https://patents.google.com/patent/US3802427A/en
US3802427A - Closed circuit, free-flow underwater breathing system - Google Patents
Method and apparatus entailing an underwater breathing system in which (1) a continuously flowing supply of reconditioned gas is supplied to a diver through...
closed circuitfree flowbreathing systemunderwatergoogle