SCBA or Self Contained Breathing Apparatus is also known as Compressed Air Breathing Apparatus or just Breathing Apparatus. This SCBA cylinder is commonly used by firefighters, rescue workers or anyone to be able to breathe air in a hazardous environment. If the SCBA cylinder is not used underwater, it is sometimes referred to as an industrial breathing set. The fact that it is self-contained means it does not need a remote supply nor does it need a long hose to provide breathable air. When used under water, SCBA is called as SCUBA cylinder or Self Contained Underwater Breathing Apparatus.
The SCBA consists of a high-pressure tank, a mouthpiece or mouth mask and a pressure regulator. These parts are all mounted and connected through a carrying frame. There are two types of SCBA namely, the closed-circuit type filters and the open-circuit industrial breathing sets.
The closed-circuit SCBA cylinder, filters as well as re-circulates gas that has been exhaled. This SCBA cylinder is used when a more enduring supply of oxygen or breathing gas is required. Cases where this type of SCBA air cylinder is useful are in mine rescue or while in long tunnels. The closed-circuit is also ideal when going through very narrow passages where a big open-circuit cylinder is not appropriate.
On the other hand, the open-circuit industrial breathing sets are made up of compressed, filtered air such as oxygen that we usually take in. The compressed are goes through a regulator then inhaled by the user. After that the gas is exhaled which depletes the air supply. Modern SCBAs are designed as open-circuit.
Usually persons involved in an open-circuit rescue carry a full-face mask, a SCBA cylinder, regulator, cylinder pressure gauge, waist belt and also a harness where the shoulder straps are adjustable. The SCBA cylinder has three standard sizes: 30, 45 and 60 minutes. The difficulty of the task and the physical fitness of the wearer causes differences in the real-life usable time that the SCBA cylinder can give air as a result the working time is often decreased by 25% up to 50%.
The SCBA cylinder may consist of steel, aluminum, or a carbon-fiber wrap. The composite cylinders are considered the lightest and due to this are preferred by fire brigades in the UK or fire departments in the United States. The only downside of SCBA cylinders is that these have very short lifespan and must be replaced after 15 years. These cylinders must also be hydrostatically tested every 5 years for metal cylinders and 3 years for composite cylinders.
For any extended operation, the empty cylinders can be replaced by new ones or fresh ones and then refilled from large tanks in a cascade manner or through an air compressor.
Just like with most air cylinders, careful handling of SCBA should be implemented because these still contain compressed gases. The compression makes the gases volatile. Being unaware of the limitations of SCBA cylinders may often lead to disastrous results causing more injuries and in some cases death.