Do you need an air purifier if you have aircon?

Air purifier vs aircon filter: what each does

An aircon filter does not clean the air as well as an air purifier, because it is not built for the same job. In practice, the mesh filter in your aircon protects the unit: it stops dust and lint from reaching the coil and keeps the airflow up. A purifier is made to clean the air in the room. NEA describes portable air cleaners as compact, stand-alone appliances designed to keep particle levels low in an enclosed space.

If you were looking for a HEPA filter aircon option, note that NEA's advice on HEPA filters is about choosing an air purifier: highly efficient filters such as HEPA are preferred for removing fine particles, and the unit should be sized for the space it serves.

The two do different jobs, so one does not replace the other. If your main concern is the aircon cooling well, the filter is what you look after. If your main concern is fine particles in the room, a purifier is the tool built for that.

What an aircon filter catches

As practical advice, the mesh filter on an aircon traps dust and lint from the room air as it is drawn into the unit. That keeps the coil and fan cleaner and helps the aircon cool as it should. It is a protective screen for the machine, not an air cleaner for the room.

Aircon filter dust builds up with use. A clogged filter cuts airflow, and with less air moving through the unit, cooling drops too. NEA advises checking the aircon filter once a month and cleaning or replacing it when necessary.

For a step-by-step method, see how to clean an aircon filter. A filter clean covers the filter only. It does not reach the coil and fan deeper inside the unit, and mould growing there is a separate problem; the guide to aircon mould explains what to do about it.

When an air purifier helps

During haze, NEA's household tips suggest closing doors and windows when the outdoor air quality appears to be worsening, and note that portable air purifiers can further reduce indoor particle levels. Fans or air-conditioners may still be used for air circulation and cooling. If your aircon draws in unfiltered outdoor air, for example a window unit, NEA advises closing the outdoor air intake.

Before you buy, check that the unit suits your room. NEA says a higher CADR means a greater ability to return clean air, that knowing the CADR and the room size helps you make an informed purchase, and that you should ask suppliers for detailed product information to check a unit's suitability.

As practical advice, a purifier can also help with smoke and pet dander in a room.

Fresh air still matters

Cleaning the air in a room and letting fresh air in are separate things. NEA's ventilation guidance says occupants of residential homes may improve home ventilation by opening doors and windows, and that fans can be used to promote air circulation when needed.

The haze advice above is for times when outdoor air quality appears to be worsening, which is when NEA suggests closing doors and windows. Outside those times, opening up the home and using a fan are simple ways to bring air in and move it around, whether or not you also run a purifier.

Running costs and servicing

As practical advice, a purifier adds a small, continuous load to your electricity use. If the model carries an Energy Label, check it before you buy. Running costs depend on the unit and how long you use it. To see how aircon and fan use compare, read aircon or fan running cost.

Your aircon still needs its own care, and a purifier does not change that. An aircon chemical wash cleans the coil and fan, which a filter clean does not reach. NEA also advises servicing aircon units regularly. The price of a wash or service depends on the job and the unit, so compare the rates companies publish for the work you need.

For what to check before and after a visit, use the aircon servicing checklist.

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