The Bushbunker: last resort wildfire protection


May 19, 2009

The Bushbunker is a purpose-built fire shelter designed to maximize the likelihood of survival regardless of the intensity or type of fire

The Bushbunker is a purpose-built fire shelter designed to maximize the likelihood of survival regardless of the intensity or type of fire

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May 19, 2009 Australia’s ‘Black Saturday’ in February claimed 173 lives and countless homes and livelihoods. The country’s worst wildfire tragedy, this horrific disaster was an extreme example of an annual threat faced not only in Australia but also North America and South Africa where similar dry conditions are experienced. As the survivors struggle to come to terms with their losses and begin to rebuild their lives, questions are being asked about what could have been done, and what must be done now to better protect populations. Tougher building standards for homes in fire-prone areas will be introduced, but another option under scrutiny is fire resistant shelters- are they safe, should governments play a role in their development and how should they be built? Entering this debate is the Bushbunker, a purpose-built fire shelter design which aims to maximize the likelihood of survival regardless of the intensity or type of fire.

There is much debate about whether or not bunkers are safe, especially as there are currently no standards in Australia governing their manufacture. Numerous companies have sprung up in the wake of the fires offering bunkers with vastly different specifications and claims, and without legislation or guidelines it’s almost impossible for consumers to know whether they’re buying a potential lifesaver or a death trap.

The Bushbunker is still very much in the conceptual development stage. The company is lobbying the government to establish standards, regulations and testing procedures and to use the Bushbunker product as a platform for the development of the relevant Australian standards and testing procedures.

What causes bushfires?

Wildfires, or bushfires as they are called in Australia, can reach incredible temperatures and burn for weeks at a time. In the Black Saturday fires the temperature reached more than 1200 degrees Celsius and wind speeds were in excess of 120 kilometers per hour.

Extreme fire weather is caused primarily by wind speed, temperature and dry air. The dry conditions experienced in many areas of Australia create lower moisture levels in ‘fuels’ such as bark, leaves and twigs, making it easier for them to ignite and burn.

Once a fire starts, wind and other weather conditions affect its intensity, direction and the speed at which it spreads. Conditions can change rapidly, making bushfire behavior difficult to predict and highlighting the importance of having a bushfire survival plan.

Climate change and the future of bushfires

A report by the Climate Institute, Bushfire Cooperative Research Centre (CRC), the Bureau of Meteorology and CSIRO in September 2007 said that Australian fire-fighters face a future of extended and more extreme bushfire weather seasons if Australian and world leaders fail to act urgently to cut greenhouse pollution.

While these fears have been echoed by others around the world, many experts are hesitant to link individual weather and extreme events so conclusively to climate change. What they will say is that it makes it more likely. Given this, Black Saturday may have given us a frightening preview of more frequent and more severe fires with very little warning time for people to escape.

Should I stay or should I go?

Everyone living in bushfire-prone areas needs a fire survival plan that includes making a decision about whether to stay and defend their property or to leave. The advice from fire experts is that if you are going to leave you should do it early, well before the fire arrives. Unfortunately, as Black Saturday tragically proved, evacuation can still be fraught with danger, especially if there is little warning of the fire's approach. Many of those who died did so trying to escape when it was too late.

Purpose-built fire bunkers aren’t designed to encourage people to stay but they could potentially provide a lifesaving, last resort alternative in situations where people are unable to evacuate.

Fire bunkers: what the experts say

As more information about the fires became available so too did amazing stories of survival, including people who had taken shelter in some sort of bunker. Professor Keith Crews of the University of Technology in Sydney, believes that concrete bunkers could help save lives.

Crews says they would need to be around two meters underground, because above ground even reinforced concrete would be likely to explode in the ferocity of fires recently experienced. In an underground bunker the earth would act as an insulator from the heat, and there’s no fuel for the fire.

The CSIRO line is still that ‘current research indicates that a well designed and prepared house can provide adequate protection during a bushfire.’ Current era bunkers haven’t been investigated by the organization but the CSIRO website lists a number of factors they say must be considered in relation to fire bunker safety including technical issues around bushfire behavior, design and construction, preparation and maintenance, intended and probable use of the bunker and establishing a safe path to the bunker.

Decisions also need to be made about when to retreat to the bunker, when to close it off, how long to remain in it and how to determine when it is safe to exit.

The Bushbunker

The Bushbunker has been designed for "maximum survivor ability no matter the intensity or type of fire” and is rated at over 4 hours with direct exposure to the fire front. Although it can be incorporated into the structure of a house, free standing, or partially buried, the company recommends it be placed completely underground to benefit from the insulating properties of the earth.

The shell is made from 300mm steel reinforced fire retardant concrete and is prefabricated using pod mass production which means it’s produced in one piece, making it structurally stronger as well as completely water and air tight. The standard model has been designed to comfortably accommodate up to six adults for more than four hours when equipped with compressed air cylinders which also provide positive internal air pressure making it impossible for poisonous gases and smoke to enter the bunker.

Two fire doors separate the entry area from the main compartment, creating an air lock which protects against radiant heat through the first steel fire door. Bushbunker says this is an important design feature, as some of the most severe burns to Black Saturday fire survivors were caused by radiant heat. Inside are flexible components such as 4 hour + rated steel fire doors, frames and sealing, bench seating, compressed air cylinders, battery powered electric lighting, storage shelving, water drums, UHF radio and Emergency Position-Indicating Radio Beacons (EPIRBs), and fire blankets and first aid materials.

The current Bushbunker product has been primarily designed for schools, local authorities and businesses, and the basic model would cost around AUD$16,000 – 20,000.

A low-end mass market product for home use called the BushbunkerMINI is also in development. To keep costs down it employs a unique DIY/owner builder system and is expected to cost around AUD$ 1,000 – 2,000.

Bushbunker hopes to have the product to market in December this year. Further information is available at

Karen Sprey


Your readers may be interested in where to get the Standard - Construction of buildings in bushfire-prone areas. See here...


There are recent amendments (or a revision edition) to this Standard that have not yet been approved by the Australian Building Codes Board for inclusion in this edition of the BCA.

Refuges, Refuge areas and bunkers as 'high protection areas' will be researched and considered as a possible addition to this Standard.

It's not in the BCA yet so you will have to buy the new one some time in the future if you think that is money well spent.


A couple of things confuse me a bit. If the pro view is any bunker needs to be at least 2 meters deep, will radio waves, regardless of type, be able to penetrate that deep? I just did a few minutes reading and it seems that radio waves can be blocked by less earth than that, my point being, what good is a radio going to be if you're dowsn in the bunker? With temperatures in the Black Sunday fire hitting 1,200C, I assume one couldn't have an antenna on the surface, unless there's some metal suitable for one that can survive those sorts of temperatures. Also, is four hours enough time to be sure it's safe to come out?

Also, and not to bad-mouth any commercial bunker producer, wouldn't a shipping container do as well if buried? It would be a lot cheaper, if it would work.

As an alternative, I read somewhere sometime back that some expert, I forget in which country, suggested an emergency balloon evacution system, one that a person would use by slipping on a harness to which the balloon is attached, step outside, then pull a cord that would almost instantly inflate the balloon and carry the person high enough up to clear any flames and at least most of the smoke. He also said the harness should have an emergency radio beacon and flashing light, like on an airplane or radio mast. Of course, anyone who had a cell phone and thought to take it could (presumably) use that. As for coming down, he said there would be a long tube coming down to the harness with a stopcock on it, allowing the person to slowly release the gas from the balloon so the person could descend once well clear of the fire. Of course, you'd need the right sized balloon for your weight -- I weigh about 85 kg, and a balloon that could all me up to a safe altitude wouldn't be safe for either someone much smaller than me, a child, say, nor for someone obese, who might go up but not far enough to be safe. (I have little idea how practical this is, so I hope I don't get flamed -- pardon the use of the term in this context! -- TOO badly! ;-)

Kurt Francis
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