Oxygen candle

An oxygen candle , also known as a chemical oxygen generator , is a device that can release a large amount of bound oxygen as part of an exothermic reaction and thus serves to supply oxygen . Oxygen generators are normally in a passive state; in this state they can be stored for years without restriction. If necessary, for example in an emergency, they are put into irreversible operation by a mechanically triggered ignition.

Oxygen candles are used in areas in which a reserve oxygen supply is necessary, which can be used with a high degree of failure safety without the supply of additional energy .

function

The oxygen is usually bound in sodium chlorate ( ), which, when ignited by a barium peroxide - iron powder mixture, reacts ${\ displaystyle \ mathrm {NaClO_ {3}}}$

{\ displaystyle \ mathrm {2 \ NaClO_ {3} \ longrightarrow 2 \ NaCl + 3 \ O_ {2}}}

decomposes, releasing oxygen. Alternatively, lithium perchlorate ( ) is used, e.g. B. is used on the ISS as an "Emergency Oxygen Pack" (EOP). ${\ displaystyle \ mathrm {LiClO_ {4}}}$

The reaction is usually triggered by a mechanical trigger. Sometimes a distinction is made between containment (steel cylinder) and briquette (charge with sodium chlorate, lithium perchlorate).

Oxygen candles based on sodium chlorate reach reaction temperatures of approx. 600 ° C, those with lithium perchlorate reach 450 to 500 ° C.

Areas of application

Chemical oxygen generator from a passenger plane

Chemical oxygen generators are used in the following areas, among others:

Submarines (especially rescue systems such as ROV Scorpio )
Space travel (e.g. Mir and ISS space stations )
Aviation (emergency oxygen systems for passengers in the event of decompression in the event of a pressure drop in the cabin)
Mining (self-rescue systems, supply of emergency oxygen through narrow supply shafts)

hazards

The problem with the use of oxygen candles is the development of heat in connection with the desired development of oxygen.

On the Mir, a defective oxygen candle almost led to disaster. The crash of ValuJet flight 592 in the USA due to the unsecured transport of old oxygen candles or an incident on the British nuclear submarine HMS Tireless in March 2007, in which two sailors were killed, also became known.

Individual evidence

^ Cord-Christian Rossow, Klaus Wolf, Peter Horst: Handbuch der Luftfahrzeugtechnik . Carl Hanser Verlag GmbH Co KG, 2014, ISBN 978-3-446-43604-6 , p. 793 ( limited preview in Google Book search).

[Cord-Christian_Rossow,_Klaus_Wolf,_Peter_Horst-1] Cord-Christian Rossow, Klaus Wolf, Peter Horst: Handbuch der Luftfahrzeugtechnik . Carl Hanser Verlag GmbH Co KG, 2014, ISBN 978-3-446-43604-6 , p. 793 ( limited preview in Google Book search).