Non-rebreather masks are designed to provide respiratory assistance.They work by supplying the wearer with oxygen and removing carbon dioxide from exhaled air.The non-rebreather mask is attached to an oxygen tank, which supplies the user with a constant flow of fresh oxygen.This allows for more precise control over the level of oxygen being supplied as well as CO2 removal rate.Non-rebreathers were invented in order to avoid rebreathing exhaled air, which can be contaminated by chemicals such as nitrous oxide or volatile organic compounds from paint fumes.It's called a "non-rebreather" because it doesn't require that you breathe into a mouthpiece like a conventional respirator does; instead, it allows you to inhale through your nose and exhale through your mouth while wearing the mask.