Radiant heat

5 min read

Radiant heat is extremely dangerous. It can kill you well before the flames from a bushfire reach you. The safest option is always to leave early. This page will help you learn how to survive radiant heat if you can't leave.

Summary

The best way to avoid radiant heat is to leave early on extreme fire risk days.
Distance is the best protection from radiant heat.
Cover up from head to toe with clothes, gloves, hat and goggles to protect your skin and eyes.
Take shelter in a building or behind a solid object or wall.

What is radiant heat?

Radiant heat is the intense heat that comes from a bushfire. Radiant heat is the biggest killer in bushfires—you can die from organ failure long before the flames reach you.

Radiant heat:

is blocked by solid objects
travels in straight lines (it can't go around corners)
travels through glass
can cause injury or even death.

[Radiant Heat]

The following may be distressing to some viewers.

Victoria is one of the most bushfire-prone parts of the world.

Every summer, bushfires threaten properties and lives, but did you know it's not the flames that kill most bushfire victims? No, it's the radiant heat.

Most victims die from the effects of radiant heat long before they're reached by the flames.

Radiant heat is what you feel when you sit next to a campfire. If a campfire heats up to two kilowatts per square metre, you'll feel that it's too hot and will want to move back from the fire. If you don't this amount of radiant heat is enough to cause burns and blisters in as little as 40 seconds.

At 12 kilowatts, it can cause some materials like dry timber to ignite.

A bushfire can reach 100 kilowatts, and the effects can be truly catastrophic.

For humans, radiant heat can cause burns from 100 metres away and cause a dangerous increase in body temperature.

Radiant heat can cause the rapid onset of heatstroke. Heatstroke damages your brain, meaning you won't be able to concentrate to make good decisions as the fire arrives. Other impacts include severe damage of internal organs and death.

There are some things you can do if you are caught in a fire, cover your skin with long-sleeved, natural-fibre clothing like wool.

It's also useful to know that radiant heat only travels in straight lines and can't bend around corners. So, sheltering behind or inside solid structures may help protect you. But be aware, radiant heat will travel straight through glass.

The best defence against radiant heat is a simple one.

If you're not anywhere near a bushfire, its radiant heat can't hurt you.

Leaving early is always your safest option.

The only guaranteed way to avoid radiant heat is to leave early, before a fire arrives.

How to survive radiant heat

Know when to leave

Leaving early on extreme fire risk days is always your safest option. Know what to do if you get caught out.

Late evacuation is extremely dangerous and can expose you to extreme levels of radiant heat. You could be seriously injured or die.

Distance

If you can't leave, the best way to survive radiant heat is to get as far away from the fire as possible. The closer you are to a fire, the more dangerous radiant heat will be. The further away you are, the less dangerous radiant heat is.

How to block radiant heat

1. Cover up

Everyone should wear clothing and protective gear that covers their entire body, from head to toe.

Do not wear a t-shirt, shorts, thongs or synthetic materials.

Protect yourself from radiant heat

What to wear for protection from radiant heat and to increase your chances of survival:

Wide-brimmed hat to protect head.
Goggles to shield eyes.
Mask or scarf/handkerchief to protect face and filter smoke.
Long-sleeved, collared shirt with the collar up to protect neck.
Long pants made from natural fibre like cotton or denim. Not stretch denim which contains synthetics that can melt onto your skin.
Tough leather gardening gloves. Not rubber or synthetic.
Sturdy boots and wool or cotton socks.

2. Take shelter

Radiant heat coming from a fire approaching a property is affecting person and their house before flames have reached them. — Radiant heat is the intense heat that comes from a fire. It can kill you. The best protection against radiant heat is distance.

A solid object, such as a brick wall or boulder can provide some protection from radiant heat.

If you can't escape the fire, take shelter:

in a building
behind a solid wall,
behind a water tank or
behind a boulder or another solid object.

Do not hide in front of a window as heat can travel through glass.

Sheltering in a car is a last resort option

Sheltering in a car is extremely dangerous. However, if you are not able to get to safety or shelter in a building, shelter in your car.

If you're forced to shelter in your car, your chance of survival is very low, but better than being in the open. To protect yourself from radiant heat:

Get down below window level as radiant heat will pass through the glass windows.
Cover yourself with woollen blankets to protect from radiant heat. Use pure wool blankets as synthetic materials will melt.

Learn more about sheltering in a car

Learn more about other last resort options

Page last updated: Wednesday, 16 September 2026 11:14:32 AM

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Radiant heat

Summary

What is radiant heat?