What are the causes of fire spread?

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A fire is a rapidly moving element that can spread quickly from one building to another. In the event a fire ignites, firefighters must be aware of the factors that cause a fire to spread quickly and work to prevent those elements from aiding in the fuel of the fire. Fire spreads by three causes: convection, conduction and radiation.


Wind is a common cause for fire to spread, especially in brush and wild fires. Wind can push fire from one burning structure to another by carrying ashes, smoke, heat and flames. It is important to remember to never start a camp fire in heavy winds where ash and sparks can fly into surrounding brush.

Chemicals, Combustibles and Accelerants

If chemicals are present in a neighbouring structure or room of a burning structure, fire can quickly spread towards those accelerants. Chemicals can include laboratory chemicals, cleansers and even paints. A combustible is an item in a structure that can trap in flames and smoke and allow the fire to reach higher temperatures and burn at a faster rate. Some common combustibles in a home fire are mattresses and sofa furniture.

Open Space

Open space provides air and free movement to flames in a fire. An open building with no doors can allow a fire to spread more quickly throughout the structure's surface than a building with doors shut. A closed door can trap a fire and prevent smoke from spreading. Buildings equipped with fire doors can also burn slower due to speciality doors that withstand the high temperatures and damage of a fire.

Construction and Ventilation Systems

The construction of a structure can cause a fire to spread. Buildings with extensive ventilation systems will burn faster because flame and smoke can travel through the ventilation to other areas of the building faster. Doors, walls and ceilings with poor insulation can allow fire to burn through them more quickly and spread to other areas of the structure as well. The materials a structure is built from can also determine how fast it will burn. According to a newsletter by Vincent Dunn of the FDNY, there are five classifications of building construction within the United States -- Fire Resistive, Non-Combustible, Ordinary, Heavy Timber and Wood Frame. Buildings constructed from wood frame and heavy timbers are more likely to allow fire to spread quickly than structures made from fire resistive or non-combustible materials.


Water is not always the best option for putting out a fire and can actually cause a fire to spread further. A kitchen fire, for example, should be put out with a special fire extinguisher or baking soda rather than water. Water can make grease in a kitchen fire splatter and spread, but baking soda or a chemical fire extinguisher can suffocate the fire and prevent it from spreading.

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