Air conditioners with air purification: what the filters actually do

What does air purification in an air conditioner actually do?

A split system recirculates room air. It draws air in across the top of the indoor unit, through a mesh filter, across the coil, and blows it back out. Anything the filter catches stays out of the room. That's the basic filtration every unit has.

Purification features add one of three things. A finer filter that catches smaller particles. An active technology, such as ions, plasma or radicals, that the maker says inhibits bacteria, mould or allergens on the filter or in the air. Or a self-cleaning routine that dries or freezes the inside of the unit so less grows on the coil and fan.

All of them only work on the air that passes through or near the unit, and only while the fan is running. Air also slips round a split's filter, because the coil and fan are designed for airflow first.

Air conditioners with air purifiers: what each brand says

This is what each maker claims on its own Australian site. We haven't tested any of it, and the features change by model, so check the specific model number on the quote.

Daikin also sells standalone air purifiers in Australia, which is why a lot of people looking for a Daikin air purifier land on its air conditioning pages. They are a separate appliance. We don't sell or rank them. You can browse every registered wall unit in our split system catalogue and compare models there.

Air conditioner vs air purifier: what a split can't do

A standalone HEPA purifier is built for one job. It pushes all its air through a dense filter, and it sits where you put it. A split's filter is looser, air bypasses it, and the unit only filters while it's running.

The official advice reflects that. NSW Health's bushfire smoke guidance suggests a purifier with a HEPA filter to remove smoke from indoor air, and adds that it has to be used in small, well-sealed areas to work well. The same page says humidifiers, negative ion generators and odour absorbers do not remove fine particles in bushfire smoke. Treat an ion or plasma feature on an air conditioner as an extra, and don't rely on it for smoke.

Are air conditioners good for asthma and allergies?

They can help by keeping humidity down and filtering some particles. The health bodies are careful about how far that goes.

The National Asthma Council Australia recommends keeping indoor humidity between 30 and 50 per cent, because dust mites and mould thrive in damp air, and notes that split and ducted systems often have built-in dehumidification. In its mould advice it suggests high-efficiency air filters, which may be built into air conditioning, heat recovery ventilation or air purifiers.

Asthma Australia's heating and cooling fact sheet says reverse cycle may help lower indoor humidity and that filters should be regularly cleaned. It also says it isn't aware of high-quality evidence that reverse cycle or refrigerated systems improve asthma symptoms. It warns that evaporative coolers can raise humidity, that unflued gas heaters release nitrogen dioxide, and that ducted heating which isn't cleaned can spread dust.

Sensitive Choice is the National Asthma Council's program for products that may help reduce exposure to asthma and allergy triggers. Daikin says its split systems and air purifiers are approved, and Panasonic says nanoe X is. The butterfly helps you shortlist. Your asthma plan still comes from your GP. For humidity control, see air conditioner vs dehumidifier, and to put the unit in the right room, get up to three local quotes.

Using an air conditioner when it's smoky outside

The Better Health Channel says split systems can be used when it's smoky outside as long as doors and windows are closed, because they recirculate indoor air. Ducted refrigerated systems work the same way. Evaporative coolers should not be used, because they pull outside air in and can replace the air in the house every two to three minutes.

NSW Health's advice is to switch the air conditioner to recirculate if it has that setting. YourHome notes that air conditioning can help filter particles from indoor air. For a bedroom during a bad smoke week, the official pairing is a closed room, the split on recirculate, and a HEPA purifier in the same room.

How often should you clean air conditioner filters?

The filter is the part of air purification you control, and a clogged one does nothing useful. Here is what the makers and YourHome say.

• Mitsubishi Electric: clean primary filters every 2 weeks in heavy use, and secondary filters every 90 days, or every 30 to 60 days with pets or poor air quality. Replace secondary filters yearly.
• LG: change or clean filters every 1 to 3 months, washing with warm water and a mild detergent and drying fully before refitting.
• Daikin, for the titanium apatite filter: vacuum it, soak it in lukewarm water for 10 to 15 minutes if it's dirty, dry it in the shade, and don't wring it.
• YourHome: clean ducts and filters in ducted systems and reverse cycle units regularly, for example at the start of the heating or cooling season.

Filter cleaning is yours. Coil and fan cleaning is a technician's job, so book a service if it smells musty with a clean filter.

Whole house air purifier: ducted add-on filtration

For the whole house, the practical option is filtration fitted to a ducted reverse cycle system. All the air comes back through the return-air grille, so upgrading the filter there treats every zone that's running.

Options include a higher-grade pleated or electrostatic filter at the return, a separate filter box in the roof, maker add-ons such as Mitsubishi Electric's Plasma Quad Connect for selected ducted units, or a ducted system with purification built in, such as Panasonic's NX Series with nanoe X. The catch is airflow. A denser filter makes the fan work harder, so the installer has to check the fan can handle it.

New, well-sealed homes may be better served by a heat recovery ventilation system, which brings in filtered outdoor air as well. Both are covered on our ducted air purification and fresh-air ventilation page. To price filtration with a new ducted system, get up to three local quotes.

What to ask for on the quote

• The exact indoor model number, and which purification features that model has. Brochures cover a range; your unit may not have them all.
• Whether optional filters are included, what they cost to replace, and how often.
• For ducted, the return-air filter type and grade, and whether the fan has been checked for the added resistance.
• Where the indoor unit goes. A split filters the room it's in, so put it in the room that matters, often the bedroom of the person with asthma.
• The dry mode and humidity settings, since humidity control does more for dust mites and mould than most filters.

A 2.5 kW bedroom split is usually $1,500 to $2,500 installed in 2026, and our split system cost guide covers what moves the price. Premium purification models sit toward the top of that range. Get up to three local quotes and ask each installer to name the filtration on the model they're quoting, then compare.