Self-contained breathing apparatus SCBA

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 SCBA is the device of choice for firefighters in fire interventions, when air becomes unbreathable due to asphyxiating or toxic fumes. The use of an ARI is not trivial: a medical certificate of aptitude and specific self-contained breathing apparatus training are mandatory.

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The open circuit self-contained breathing apparatus

Several essential pieces of equipment make a self-contained breathing apparatus:

The harness: this is the central part of the SCBA. It holds the compressed air cylinder and has a double trigger system, an available-air pressure gauge and a low pressure whistle to warn the user when the air reserve is almost empty. The SCBA harness generally has padding to provide more comfort during use.

The compressed air cylinder: they come in different sizes depending on the required use duration (200 or 300 bars). They can also be made of carbon fiber in order to considerably reduce weight, even if the standard is the steel cylinder.

The face piece: a full face mask fitted with a on-demand valve. There are many types of SCBA masks: full face mask with harness or net, with or without F1 attachment (fire helmet), etc. The face piece selection (most generally a full face mask) is essentially based on the concerned activity sector and on incurred risk.

The closed circuit self-contained breathing apparatus

Unlike open circuit self-contained breathing apparatus, there are also closed circuit SCBA, in which air circulates in a closed loop, i.e. the user always breathes the same air treated and enriched with oxygen.

The exhaled air (in a bag) is purified (carbon dioxide being trapped by a chemical) and enriched in oxygen: the complement between the oxygen content of the exhaled air and the breathable air is chemically supplied (super potassium oxide - KO2) or simply added oxygen (pure oxygen cylinder).

As with conventional open circuit SCBAs, there are two categories of closed circuits self-contained breathing apparatus: equipment for on-site interventions and rescue equipment for emergency evacuations (also called self-rescuer masks or escape mask).

The rescue or escape SCBA

Particularly simple, easy and quick to use rescue or escape SCBAs offers uncontaminated breathing air over a fixed period of time (generally quite short around 20 to 30 minutes) allowing emergency evacuation in maximum safety. It can only be used as an emergency evacuation device, in no case for on site intervention or to rescue a person in difficulty.