What Are the Causes of Fire Spread?

Your home is your castle, but it is not an impenetrable fortress. Knowing the causes of fire spread can help prevent and protect your home before a fire starts. For a fire to start, it needs heat (such as a spark or warmth radiated from a hot surface), oxygen (the air we breathe) and fuel (things that burn, from solids to gases). Firefighters study and research the methods that heat may transfer in order for a fire to burn so that they know exactly how to put out the flames.

Orange flame at gas stove
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What Are the Causes of Fire Spread?

Conduction Fire

When heat or electricity is transmitted through another substance, that is called conduction. This process can move energy through the home, but it can also be the heat source for a fire. Metal conducts heat, and most metal in the home is used in things like ducting. Items that can catch on fire – called combustibles – that are in contact with something conducting heat have one element needed to start a flame. In your home, walls are built as insulators, the opposite of a conductor, to retain heat and slow the rate that fire can spread.

Convection Fire

A fire that is spread from a heat transfer to liquids and gases is called a convection fire. Heat rises into the air, reaching the ceiling of whatever room it is in. This is pleasant when controlled for a cold night, but dangerous when the heat source caused a fire. When a fire starts, it sends gases into the air. These gases will travel through the house on air currents and meet cooler air carrying oxygen. Extreme heat and oxygen combined with combustible materials is the recipe for a fire. And when the heat reaches the ceiling, the mix of heat and gases spreads the flames to other rooms.

Radiation Fires

Fireplaces and heaters are often described as "radiating heat." A radiation heat transfer is when those rays of heat from a fire combine with a combustible material. Heat plus fuel in a livable room filled with oxygen? Fire. Heat travels in a direct straight ray from its source. Moving combustible items away from heat is the simplest way to prevent an accidental fire.

Spread by Water

Sometimes the typical cure for a fire can be its cause. Oil and water do not mix. When cooking oil and grease are the combustible materials for an oven or stove heat source, water will not put the fire out. Grease fires can be spread by water splattering the lit grease on to other surfaces, such as wooden cabinets or dish towels. The fire then catches further, and can cause a convection fire when the heat rises. A fire extinguisher should be in the kitchen for emergencies. Baking soda will also suffocate a grease fire.