SummaryRead the full fact sheet
- Not all air conditioners are safe to use when it is smoky outside, such as during a bushfire.
- Some air conditioners can draw in smoky air from outside, which can be harmful to your health.
- It’s important to understand the type of air conditioner you have so that you know if, and how, to use it when it’s smoky outside.
About air conditioners
There are 2 main types of air conditioners:
- air conditioners that introduce external air
- air conditioners that only recirculate internal air.
It’s important to understand which type of air conditioner you have so you know if, and how, to use it when it’s smoky outside.
Which air conditioners can be used when it’s smoky outside?
Do not use air conditioners that draw in air from outside when it is smoky outside.
You can use air conditioners that only use internal air (ones that re-circulate/re-use indoor air and do not draw in air from outside).
|Air conditioner type||Can it be used when it’s smoky outside?|
|Split systems |
– including central ducted
|Window/wall box unit |
– outdoor air vent ‘closed’ or ‘fresh air’ function off
– ‘fresh air’ function off, if present
|Portable refrigerated, single hose||✗|
|Portable refrigerated, 2 hose |
– ensure the seal around the window vent kit is tight
|Portable evaporative |
Understand the type of air conditioner you have
There are 2 main cooling technologies used in air conditioners:
- evaporative cooling.
Refrigerated (and reverse cycle) air conditioners can be further classified into:
- split systems (wall or ceiling mounted)
- window/wall units
- portable units.
Evaporative coolers are either roof mounted or portable.
Split systems can be used when it’s smoky outside provided all external doors and windows are closed.
If your air conditioner has an outdoor unit and an indoor unit (either in the roof or on the wall), you have a split system.
Split systems are the most common types of air conditioners in Victoria. Using the refrigeration cycle, reverse cycle units can both cool and heat.
Large cassette units (typically found in offices and warehouses) can have ‘fresh air’ or ‘ventilation’ functions which draw in outside air.
When it’s smoky outside, cassette units should have any ‘fresh air’ or ‘ventilation’ function switched off to prevent drawing in smoke from outside.
Evaporative air conditioners
Evaporative air conditioners should not be used when it’s smoky.
If your air conditioner consists of one unit (often on the roof) connected to a series of ducts with vents in the ceiling, you have an evaporative air conditioner.
Evaporative air conditioners, also called evaporative coolers, use water to cool outside air before it is sent into the home through vents.
Evaporative air coolers should not be used when it’s smoky outside as they will quickly draw smoke inside the house leading to poor indoor air quality. When in use, evaporative coolers can completely replace the air in the house every 2 to 3 minutes.
Window/wall (box) unit
Window/wall units can be used when it’s smoky if the outside air vent is ‘closed’, meaning only indoor air is recirculated. They should not be used when it’s smoky outside and the outdoor air vent is ‘open’. This vent may be controlled manually or through a ‘fresh air’ or ‘ventilation’ function in the unit’s settings.
If the unit sits within a window or wall, you have one of these air conditioners.
Rarely, these units can be evaporative coolers. If your unit has a water supply, it is an evaporative cooler. Evaporative coolers draw in outside air so they should not be used when it’s smoky.
Portable air conditioners
If your air conditioner can be moved around (for example if it is on wheels), it is a portable air conditioner. Portable air conditioners may be either refrigerated or evaporative.
These have either one or 2 venting hoses (often placed through an open window) for venting hot air out of the home. These hoses are not for bringing outside air into the home.
Single-hose units should not be used when it’s smoky. Single-hose units take air from inside the room but don’t replace it all, creating a negative pressure in the room with the unit.
This means air can be drawn into the room from other areas of the house and from outside if any windows or doors are open or other gaps (for example, under doors or through vents or open chimney flues) are present.
Two-hose units can be used when it’s smoky. Two-hose units work differently. Air drawn from inside the room is cooled and returned into the room which avoids air being sucked into the building. While outside air is used by these units, it is kept separate from the internal air flow and not drawn into the room.
Portable evaporative coolers can be used when it’s smoky. Portable evaporative coolers only circulate indoor air, provided external doors and windows are sealed.
Staying informed during smoke events
Visit the Victorian Department of Health’s social media channels for information: