Unless you take preventive measures and install ember screens, a roof-mounted evaporative air conditioning unit poses a fire hazard to your home during a bushfire.
It might seem improbable that evaporative air conditioners, which require continuous wetting of the filter pads, make your home vulnerable during a bushfire.
However, the severe bushfire that ravaged Kelmscott and Roleystone in February 2011 and destroyed over 70 homes shows this to be the case.
Investigations by the Department of Fire and Emergency Services (DFES) revealed that half the homes caught on fire due to an ember attack.
During an ember attack, embers and other hot debris blown from a bushfire fall on the flammable filter pads, causing the unit to burst into flames.
Therefore, you must tune your evaporative aircon and ensure it’s in tiptop condition at the onset of every bushfire season.
Why Does It Matter?
The filter pads in an evaporative cooler comprise a combustible cellulose material.
Evaporative coolers catch on fire if they draw sparks and embers from the air or if embers land on dry filter pads.
When the dry filters ignite, the flames spread to the rest of the house from the roof.
Fires starting in the evaporative air conditioners are difficult to extinguish, even for seasoned firefighters. The fire burn through the dry ceiling boards before the entire structure falls into the building.
In such instances, the entire building might ignite, resulting in extensive damage or total loss.
During a bushfire, the wind can send embers and hot ash several kilometres ahead of the main fire. The flying, hot debris pose a fire risk for your home even when you’re not in the direct line of a bushfire.
Your home is especially vulnerable during Fire Weather Day with a very high Fire Danger Rating because power companies often cut the power.
Cutting the power during catastrophic fires eliminates the risk of fire spreading through the powerlines. But it results in power outages and lengthy interruptions.
Power blackouts mean you can’t run the evaporative air conditioning unit and keeping the filter pads wet.
Dry filter pads on an evaporative unit make your home vulnerable to an ember attack.
Bushfires generate copious amounts of smoke and cause air pollution, resulting in the air quality dropping to hazardous levels.
On top of the smoke, bushfires lead to fine particle air pollution, which poses a grave danger to human health even during short exposures.
Fine particle air pollution contributes to chronic heart and lung conditions. It also aggravates pre-existing respiratory and heart diseases.
To protect your family from the adverse effect of dropping air quality, you need to take these precautions:
- Shut your windows and doors. Keeping your home smoke-free is the most efficient way to preserve your indoor air quality. Keep all your windows and doors closed long before the hazy days.
- Ensure the home is well sealed. Sealing the house preserves the air quality by ensuring that smoke doesn’t get in. Block major drafts with draft excluders and plug gaps in the walls and eliminate spaces under the windows and doors. A properly sealed home has lower heating and cooling needs and will lower your heating bills.
Clearing the Smoke
If smoke gets inside your home, you need to clear it as quickly as possible.
- Use an air purifier. Air purifiers with HEPA filters are a quick and effective way to rid your home of bushfire smoke.
- Use the air conditioner. While air conditioners are best suited to filtering dust and pollen, not filtering smoke, they help to improve air quality.
Using an Evaporative Air Conditioner During a Bushfire
If you are unfortunately in a situation where you need to prepare for a bushfire here’s what to do with your AC unit if your home uses an evaporative air conditioner. You’ll need to tread carefully since they’re vulnerable to ember attacks. At the first signs of bushfire smoke, you should:
- Get the unit running to keep the filter pads wet.
- Switch off the air conditioner. If the house is engulfed in smoke or hot ash starts raining down around it. That keeps the unit from sucking smoke, hot ash, and embers into the house. Defending your house during a bushfire isn’t advised, evacuating is always the safer option. Do this only if you have no other choice than staying.
- Keep the filter pads wet. If the unit can run water over the filter pads when the fan is turned off, let it do so. During power failure or if your unit can’t run the water, wet the filter pads with a garden hose.
Monitor the air conditioner and the area around the home to prevent spot fire until the danger of an ember attack passes.
How Can You Protect Your External Unit from Embers?
To protect your evaporative air conditioner from destructive embers, the Department of Fire and Emergency Service recommends installing ember protection screens.
Evaporative air conditioners are especially vulnerable because they sit high up your roof, and their filter pads comprise a flammable cellulose material.
That increases the likelihood of an air conditioner drawing embers from the air, which can then ignite the flammable filter pads. When filter pads ignite, the evaporative air conditioner may collapse into your roof, causing the fire to spread into the rest of the house.
Protect Your Evaporative Air Conditioning Unit from Ember Attacks
Ember protection screens prevent embers from entering a roof-mounted evaporative air conditioner and igniting the filter pads. The screens are made of corrosion-resistant bronze, steel, or aluminium mesh with a maximum aperture of 2 mm.
When installed, ember screens eliminate the fire hazard without affecting the cooling unit’s performance or abilities.
Research by the University of Western Australia affirms that ember screens protect air conditioners from ember attacks without limiting their operating range.
Since evaporative air conditioners come in various shapes and sizes, there isn’t a standard ember screen on the market.
However, the DFES recommends three types of ember protection screen designs:
- Unit covers. It’s built to fit over the entire evaporative air conditioning unit. The whole unit cover must be sealed, including the bottom, to eliminate all ember entry points.
- External ember screens. External screens fit over individual air intake panels and are the most effective option. They must fit snugly over the unit and any gaps greater than 2 mm sealed with a fire-resistant sealer or foam.
- Internal ember screen. Internal screens fit inside the evaporative unit between the filter pads and air intake panels. While beautiful, these screens offer inferior and pose a fire risk. Embers can still land on the air intake panel’s ledge and ignite the filter pad through the net.