Self-contained breathing apparatus

Self-contained breathing apparatus, SCBA – or more precisely open-circuit self-contained breathing apparatus (OC SCBA) – are personal protective equipment made for use when the oxygen rate in ambient air is under 19.5% of the volume (presence of asphyxiating gas or fumes), in presence of irritating gases or when the pollutant concentration exceeds 60 times its occupational exposure limit value (OEL). The use of an SCBA respirator implies first to follow specific SCBA training.

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Open-circuit self-contained breathing apparatus - OC SCBA

A self-contained breathing apparatus is composed by several fundamental components:

A harness: this is the key element of the system. Its role is to maintain a compressed air cylinder and it features a dual trigger system, an available air manometer and a low-pressure whistle to alert its user in case of poorly filled cylinder. It is usually padded to bring more comfort when operating.

A compressed air cylinder: they are available in different sizes according to the operating time needed (200 or 300 bars). Cylinders can also be made of carbon fiber in order to considerably reduce their weight. The classic version still remains made of stainless steel.

A facepiece: the SCBA’s full face mask is equipped with a lung demand valve unit. There are many types of masks such as full face masks with harness or net, with or without F1 fixation (firefighter helmet)… Choosing the proper facepiece – usually a full face mask – essentially depends on the application, the field of activity and the potential hazard.

Closed-circuit self-contained breathing apparatus - CC SCBA

Contrary to the open-circuit self-contained breathing apparatus (OC SCBA), there are also closed-circuit self-contained breathing apparatus (CC SCBA), in which air flows in a closed loop. This means that the user always breathe the same air that is processed and re-oxygenated.

Expired air is stored in a bag then purified – carbon dioxide being trapped by a chemical product – and re-oxygenated: the complement between the expired air’s oxygen rate and the breathable air is chemically produced (super potassium oxide - KO2) or simply provided with a pure oxygen cylinder.

Just like classic OC SCBAs, there are two categories of CC SCBAs (closed circuit): self-contained breathing apparatus for on-site interventions and emergency escape breathing devices (EEBDs and self-rescuer mask or escape mask).

Emergency escape breathing devices

Particularly simple, easy and fast to use, self-contained emergency escape breathing devices (EEBDs) provide clean breathable air on a determined period (usually quite short between 20 and 30 minutes) in order to safely enable emergency evacuations. They can only be used in emergency evacuation situations and never to operate on site or to rescue someone in trouble.

See the Emergency escape breathing device page