WW1: Aviator's oxygen mask in position and ready to use. Note the handwritten caption on the photo. WW1 planes could not safely fly at 10,000 ft, ceiling for deploying oxygen masks, so the development of the device looked at the future.
Oxygen Delivery System: Room air is 21%..Oxygen mask may deliver up to 100% O2. Partial rebreather mask 8-11 L/m conserves about 1/3 of your exhaled air; should deflate slightly. Nonrebreather used to counteract smoke inhalation/ any short term therapy requiring 80-100% O2. Shouldn't deflate. No more than 3 L/m for COPD pts. Ventimask delivers exact low flow conc of O2. Provides air-O2 mixture.