SCBA (Self Contained Breathing Apparatus)
A self-contained breathing apparatus (SCBA) is designed to be a type of mobile air supply. High-altitude pilots, mountaineers, medical rescue teams, firefighters, miners, and personnel working in hazardous areas that are filled with toxic gases use SCBA equipment. This type of respiratory protection is also commonly referred to by the names "emergency escape breathing apparatus," and "industrial breathing sets." SCBA should not be confused with SCUBA, which stands for self contained underwater breathing apparatus, which is a similar type of device that is worn by underwater divers. There are open circuit SCBAs and closed circuit versions.
Open circuit models are filled with filtered compressed air. This type of SCBA has a full face mask, a regulator, an air cylinder , a cylinder pressure gauge , and a harness that has adjustable shoulder straps and a waist belt so you can wear the device on your back. The air cylinder can only hold a certain amount of air, which is about 30 or 45 minutes worth. However, it can be less or more time. The air cylinders can get heavy as they are made out of aluminum, steel, or of a composite material. Composite air cylinders are definitely the lightest in weight, but they also have the shortest lifespan. All types of air cylinders need to be hydrostatically tested every three to five years, depending on what they are made of.
Most types of SCBAs are the positive pressure type. These devices feed a steady stream of air to help stop toxic fumes and smoke from entering into the mask. This apparatus is designed to force clean air into the gas mask by using positive pressure. Since the air in the tanks is under pressure, there is no undue effort required by the personnel to breathe. The system is called positive pressure because the air inside the mask is greater than the ambient temperature. However, not all SCBAs are this type. Another form of SCBA is called the demand type. These devices are designed to supply air on demand. Firefighters and people who work in toxic environments are required to use positive pressure SCBAs for safety purposes.
A closed circuit model is a special SCBA which recirculates exhaled gas. These models are generally used when a longer supply of air is needed. Firefighting SCBAs need to be heat resistant and in the U.S., the devices of safety gear that are used for firefighting need to meet standards that are established by the National Fire Protection Association, NFPA Standard. Anybody who uses SCBA should be properly trained in the equipment.