The Full Form of SCABA is‍ Self-contained breathing apparatus.

Self-contained breathing apparatus (SCBA) are used to protect users against oxygen deficiency, dust, gases and vapors at plants, aboard vessels, at fire and in tunnels.
Ever since they were first introduced onto the market in 1949, SCBA has been widely used in such fields as firefighting, rescue operations, escape training at fire stations, iron works, chemical plants, nuclear facilities, hotels, etc. throughout Japan.
The apparatus can be used even if in the oxygen deficiency or unknown the contaminants.
SCBA has the air breathing apparatus and oxygen breathing apparatus.

The SCBA supplies the compressed air from the air cylinder to the wearer through cylinder valve, pressure reducer, pressure demand valve or demand valve.
Exhaled air goes to the atmosphere through exhalation valve.