Tuesday 8 January 2008
Video
Advice for people trapped in their cars during a bushfire has been
updated with a groundbreaking study into what happens to a vehicle
caught in the middle of a firestorm.
The research initiated by NSW Rural Fire Service and conducted
by Bushfire Cooperative Research Centre with CSIRO scientists,
sought to determine the maximum heat load that a vehicle could face
while remaining a safe haven for its occupants, both in terms of
the air temperature and the air quality inside the vehicle.
The study of burnovers in civilian passenger vehicles was conducted
in January 2007 at the NSW Rural Fire Service Hot Fire Training
Facility in Mogo, on the New South Wales south-coast. Seven used
cars were subjected to burnover conditions with a gas flame front
simulator. The two-wheel-drive sedans, which ranged in size, age
and make, were donated by the NRMA.
Each car was fully instrumented with sensors to monitor for air
toxics and heat levels at many points inside the vehicle including
above and below the window height, front and rear seats and, above
and beneath a woollen blanket. Comparisons were made between having
the air conditioner on or off, and by facing the car forwards,
side-on or backing to the flames.
The research made several key observations:
- Using a woollen blanket for shelter in either the front or rear
foot-well of a vehicle is the most effective strategy to reduce
exposure to both toxic gases and high temperatures.
- Facing the front of the car towards the approaching fire was
better than side or rear orientation.
- Direct flame contact from either the passing fire front or from
burning ground fuels makes the vehicle almost immediately untenable
for occupants.
- Testing under a wide range of conditions (slow/fast burn,
front/rear/side orientation, etc) found that the rise in air toxics
inside the vehicle was the main reason the car became unsuitable
for its occupants.
- Thermoplastic body parts and the structural design features of
different vehicles contributed to the varied performance of cars in
burnover conditions with the more recent models performing
worst.
- Operating an air conditioning system in recirculation mode
reduces temperature exposure in all but extreme conditions and may
add to your comfort in the early stages of exposure. However, air
conditioning will not increase your chances of survival, on or
off.
- There was no significant involvement of the cars fuel systems
in any of the experiments. (None of the cars tested had plastic
fuel tanks).
Lead researcher Justin Leonard, from CSIRO Sustainable
Ecosystems, said the range of temperatures inside the vehicles was
considerable.
“Some tests recorded peak temperatures up around 300C in
parts of the cabin but at the same time down low under the woolen
blanket the temperature was around 40 to 50 degrees, which is quite
survivable. Even when blankets were not used sheltering below the
window level in the front and rear foot wells was the best
strategy”
Mr Leonard said the smoke and toxic gases inside the melting
cars was often more significant than the heat.
“Many cars are lined with PVC materials and when that is
heated, even before it ignites, it will release hydrogen chloride
gas. That is a severe irritant and this could cause people to panic
and get out of the vehicle.”
The Australasian Fire Authorities Council (AFAC), the peak body
for the fire and emergency services, has used this research to
refine its guidance for people in vehicles during bushfires
These guidelines were previously based on evidence gleaned from
tragedies from the fireground, the observations of emergency
service workers and from limited tests on vehicles in the
1960s.
The guidelines were sound but there remained uncertainties on
some factors including the construction and materials of modern
vehicles and the influence of protective actions taken by
occupants. (For example, having the air conditioning on or off, the
orientation of the car to the fire front, seeking protection under
woolen blankets, or seeking refuge in various parts of the
car’s interior.)
The Chief Executive Officer of AFAC, Naomi Brown, said this
research provided a better understanding of what happened to
vehicles in bushfire conditions. Fire agencies and emergency
services would use this research as a basis for their community
safety campaigns.
“It is with extreme caution that people should be given
advice about taking refuge in their vehicle in a bushfire. This
research shows that sheltering inside a vehicle is a high risk
strategy and that it is highly unlikely that a person will survive
in all but the mildest circumstances.”
““Whilst sheltering inside a vehicle offers a
slightly higher chance of survival than being caught in the open,
the current policy of preparing your home, and deciding early
whether you stay or go, is a much safer option. It is essential
that all people likely to be exposed to bushfire risk realise
this.”
Naomi Brown and Justin Leonard are available for
comment.
High resolution video DVDs are available for media.
For more information contact:
David
Bruce, Bushfire CRC Communications Manager
Ph: 0414 223 281.
Jay Gleeson, AFAC Communications Manager
Ph: 03 9418 5203
