How Bushfires Start
Bushfires and grassfires start due to natural and human causes. Fire needs heat, oxygen and fuel (vegetation) to start and keep burning. Learn more about what causes bushfires and how to prevent bushfires starting on this page.
Bushfires start due to natural and human causes
Learn more about how fires start and spread in the video below.
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Lightning strikes are the most common cause of bushfires
Lightning is the most common cause of bushfires and grassfires in Australia.
More than 90% of the area burned during the Black Summer 2019-20 bushfires can be traced back to fires started by lightning.
Because lightning is common and out of your control, you need to be prepared for bushfires to happen at anytime. Stay across any fires in your area with VicEmergency and make sure you have a fire plan.
Human causes of bushfire
People can also start fires, either accidentally or on purpose.
Bushfires can be caused by:
Fires can also start due to sparks from:
You can prevent bushfires starting by being fire safe when exploring the outdoors, holidaying in the country, or working on the farm.
Fire Science: the fire triangle
Fire needs three things to exist: fuel, heat and oxygen.
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Fire is a chemical reaction. Three things are needed for fires to start, burn and keep burning.
1. Fuel (vegetation)
A fire needs something to burn.In bushfires, this is vegetation—trees, bushes, plants, grass—and other structures or objects like houses or sheds.
2. Heat
A fire can't start or continue to burn without heat. Heat sources that can start a fire include lightning, campfires, car exhaust and cigarettes.
Once a fire starts, the fire itself becomes the heat source that keeps the fire going.
3. Oxygen
A fire can't burn without oxygen. Oxygen is part of the chemical process that creates fire.
Remove fuel, heat or oxygen to put the fire out
If any one of the three ingredients of a fire is removed, it will go out.
1. Fuel is removed
If there isn't enough vegetation for a fire to burn, it will eventually go out. Firefighters create breaks in vegetation (fire breaks) on purpose to stop fire spreading.
Prune and remove vegetation on your property to stop fire reaching your home.
2. Heat is removed
For example, putting water on a fire cools it down and puts it out.
3. Oxygen is removed
For example, firefighters use foam to stop a fire getting more oxygen. Fire blankets are used in kitchen fires for the same reason.
Take care not to start a bushfire
Causing a bushfire is a serious crime. It's a crime even if you didn't mean to start one.
Penalties for recklessly causing a bushfire or grassfire include up to 15 years’ imprisonment.
Reckless behaviour can include:
- leaving campfires burning
- burning off without a permit
- using hot tools or machinery on Total Fire Ban days.
The maximum penalty for deliberately starting a fire resulting in death is 25 years’ imprisonment.
If you see reckless or intentional behaviour that could lead to a bushfire, report it. Contact Crime Stoppers on 1800 333 000.