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.