The Non Rebreather Masks are the masks that do not allow rebreathing of the gases to take place when a patient is ventilated or he takes spontaneous breaths while the mask is being held.
These masks of Non Rebreather type need to have a very high flow of oxygen as most of the oxygen is being lost. A major amount of the oxygen flow is left out in the open air and hence cannot be salvaged.
This increases the wastage of the gases as well as the cost incurred in supplying the gasses especially oxygen. The oxygen cylinder may also get frequently exhausted when the Non Rebreather Masks are used due the large volume of wasted oxygen.
The Non Rebreather Masks can deliver up to 80% of oxygen. This is sufficiently good compared to the other types of oxygen masks that sometimes provide lesser concentration of inspired oxygen.
Another advantage of the Non Rebreather Masks is that as there is no rebreathing of the exhaled gases, carbon dioxide and other waste gases are expelled effectively, thus hypercarbia can be easily be prevented.
A rebreathing mask in comparison to a Non Rebreather Masks can even deliver up to 100% oxygen depending upon how tightly it is fitted.