A<unk>  <unk> ,<unk><unk> ,<unk><unk>  facemask, etc.) is a device used in medicine to assist in the delivery of oxygen therapy. A<unk>  requires that the patient can breathe unassisted, but unlike a low-flow nasal cannula, the<unk>  allows for the delivery of higher concentrations of oxygen. An ideal<unk>  does not permit air from the surrounding environment to be inhaled, hence an event of a source gas failure (i.e. the oxygen cylinder being drained completely) is life threatening.
Non-rebreather mask
Oxygen mask
Gas mask
Venturi mask
Oxygen tent
N95 respirator
Elastomeric respirator
Non-invasive ventilation