Oxygen candles generate breathable air through a controlled chemical reaction, providing a self-contained and immediate oxygen source. They are valuable in environments where external oxygen is unavailable or compromised. This technology is used in various specialized applications, offering respiratory support when other systems might fail.
What Is an Oxygen Candle
An oxygen candle, also known as a chlorate candle or chemical oxygen generator, is a solid-state device that produces oxygen through a chemical process. It consists of a steel canister containing a mixture of chemical compounds. The primary oxygen-generating chemical is often sodium chlorate (NaClO₃), though potassium chlorate or lithium perchlorate can also be used.
This chemical is combined with a fuel, commonly iron powder, and a catalyst such as barium peroxide (BaO₂) or other metal oxides. The mixture is compacted into a solid block and sealed within its casing. This unit does not rely on external air or power, making it a reliable oxygen source.
How Oxygen Candles Work
The oxygen candle’s operation begins with an initiation mechanism, such as a firing pin or igniter, which applies localized heat to the chemical mixture. This initial heat causes the iron powder to burn, generating significant heat, typically around 600°C (1,112°F). This exothermic reaction sustains the subsequent decomposition.
The heat from the burning iron then triggers the thermal decomposition of the sodium chlorate. Catalysts like barium peroxide or iron itself lower the temperature required for this decomposition to occur efficiently. During this process, sodium chlorate breaks down into sodium chloride (common salt) and releases gaseous oxygen. The chemical reaction is: 2 NaClO₃ → 2 NaCl + 3 O₂. This continuous, self-sustaining reaction produces a steady flow of oxygen without consuming outside air.
Common Uses and Safety Considerations
Oxygen candles serve as emergency or supplementary oxygen sources in various enclosed environments. They are used in commercial aircraft for emergency passenger oxygen systems, deploying automatically during cabin depressurization. Submarines and spacecraft, including the International Space Station and past Apollo missions, also utilize them as a backup or primary means of oxygen generation. They are also employed in mine refuge chambers and emergency breathing apparatuses, providing breathable air in hazardous conditions.
Despite their utility, oxygen candles present specific safety considerations. The chemical reaction generates substantial heat, with the outer casing temperature potentially reaching up to 600°C (1,112°F). This heat necessitates careful handling and proper insulation to prevent burns or ignition of nearby materials. Mishandling can lead to fire hazards, and once initiated, oxygen production cannot be stopped until the chemical mixture is exhausted. Proper storage in cool, dry areas and adherence to disposal regulations for hazardous materials are important.