Should you run the evaporative cooler when there's smoke outside?

An evaporative cooler blows outside air over wet pads to cool it, then pushes that air through the house and out through open windows and doors. That constant flushing is why it works so well on a dry northerly day. It's also why it struggles when the outside air is the problem: whatever is in the air outside, the cooler delivers to every room.

Refrigerated air conditioning works differently. A split system, and most home ducted reverse-cycle systems, take air from inside, cool it over a coil and send it back, with doors and windows closed. Outside air doesn't pass through the house; the system moves heat out through the outdoor unit. Some systems have a fresh-air or ventilation function, and that part does bring outside air in.

Victoria's Better Health Channel says evaporative air conditioners should not be used when it's smoky, because they quickly draw smoke into the house, and notes they can replace the air in a home every two to three minutes. It says split systems can be used when it's smoky outside provided external doors and windows are closed, and that units with a fresh-air or ventilation function should have it switched off.

Haze reaches Melbourne's west from bushfires, planned burns and sometimes industrial fires. Fine particles in smoke are the main health concern, and people with asthma or heart or lung conditions, older people, young children and pregnant women are usually most affected. Follow the health and EPA advice on the day, and if smoke is making someone unwell, get medical advice.

Turn the evaporative cooler off, including fan-only mode, and close the windows and doors you'd normally open for it. That leaves the house sealed but without cooling, which is fine on a mild smoky day and hard going on a hot one.

On a hot, smoky day the best option is a closed room with refrigerated cooling. If you have a split system in a bedroom or living area, shut that room up and run it in cool mode. Fans don't remove smoke, but they keep air moving in a closed room on a warm day. Check on neighbours and family who are more at risk from smoke and heat.

Many homes in Melbourne's west have ducted evaporative cooling and no refrigerated air at all. One split system in the main bedroom or living room gives the household a cool, closed retreat on smoky days, on muggy days when evaporative cooling struggles, and efficient heating in winter. It doesn't mean giving up the evaporative system for the dry heat it handles well.

Other households replace an ageing evaporative system altogether. Converting to ducted reverse-cycle means removing the roof unit and installing an indoor unit, an outdoor unit and new insulated ducts, because old evaporative ducts rarely suit refrigerated air. It's a bigger job, but it gives cooling that works with the house closed and heating for the whole home. Our guide to evaporative versus refrigerated cooling compares the two through the year.

Once the air outside has cleared, open the house up and air it out. If ash has fallen, have the cooler's pads and water reservoir checked and cleaned before its next long run. Pads can hold the smell of smoke for a while, and ash in the water ends up blowing through the house. Don't climb onto the roof to check the unit yourself.

Clean split system filters after heavy use on smoky days too. The Victorian Government suggests cleaning reverse-cycle dust filters about twice a year, or more often with heavy use, and dirty filters cut airflow and efficiency.