Oxygen gas itself is not flammable or combustible. It does not burn when exposed to a flame or ignition source. Instead, oxygen plays a different role in the process of fire. It supports and intensifies the burning of other materials.
What Flammability Means
Flammability refers to a substance’s ability to ignite easily and sustain a flame, acting as the fuel in a fire. A flammable material, whether solid, liquid, or gas, undergoes rapid combustion when exposed to an ignition source. For a fire to occur, three components must be present simultaneously: heat, fuel, and an oxidizing agent, typically oxygen. This concept is often called the “fire triangle.”
Oxygen’s Role in Fire
Oxygen’s role in a fire is not as a fuel, but as an oxidizer, enabling and intensifying combustion. Combustion is a chemical process where a substance reacts rapidly with an oxidizer, releasing heat and light. Oxygen accepts electrons during this chemical reaction, facilitating the breakdown of the fuel and the release of energy. Without oxygen, most fires cannot start or sustain themselves.
The concentration of oxygen directly impacts how intensely a fire burns. For example, while air contains about 21% oxygen, a fire typically requires at least 16% oxygen to sustain combustion. An increased oxygen concentration can make fires burn hotter and faster. Materials that might not burn in normal air can ignite vigorously in an oxygen-rich environment.
Safe Handling of Oxygen
Given oxygen’s ability to support combustion, safe handling and storage are important. Oxygen cylinders should be kept away from heat sources, open flames, and flammable materials. Even substances like oils, greases, and certain aerosols can become dangerous fuels in the presence of concentrated oxygen. Proper ventilation is also important, as small leaks from oxygen systems can create an oxygen-enriched atmosphere, making a fire hazard greater.
High-pressure oxygen cylinders require care; they should be stored upright and secured to prevent them from falling. Keep cylinder valves and connections clean, as contaminants like dust, dirt, or oils can pose fire hazards. Opening cylinder valves slowly helps prevent rapid pressurization, which can generate sufficient heat to ignite certain materials. Adhering to these precautions helps manage the risks associated with oxygen’s oxidizing properties.