If the atmosphere you want to enter or work in is a danger to life or health a conventional respirator or mask will probably not be suitable protection. You will need a Self Contained Breathing Apparatus (SCBA) or, more simply, BA.
BA equipment is “self contained” because it does not rely on a remote supply, either through a hose or the surrounding atmosphere itself. This breathing system provides clean and safe breathing air. It is primarily used by rescue workers, fire fighters and industrial workers.
BA set components
The three main components are the high pressure cylinder or tank, the pressure regulator, and the inhalation connection / device. This might be a mouthpiece, mouth mask or face mask. BA sets can be integrated into gas tight suits.
Breathing apparatus sets need to be constructed from carefully selected materials depending on the application they will be used in (fire fighting, mining, diving, etc). If a set has been designed for use underwater they are referred to as self-contained underwater breathing apparatus (SCUBA).