Air conditioning filters explained
By the A.C. Wilgar air conditioning team · Last updated October 2026
Quick answer: every split air conditioner has washable filters that trap dust, hair and pollen as room air passes through the indoor unit. Many models add extra filtration or air purification technology. Clean the main filters every two to four weeks when the system is in regular use, and have the system serviced once a year.
What air conditioning filters do
A split air conditioner recirculates the air in your room. Air is drawn into the indoor unit, passes through the filters and over the coil, and is returned to the room cooled or warmed. The filters protect the coil and fan from dust and capture particles from the air on the way through.
A split system does not bring fresh air in from outside, so it is not a replacement for ventilation. It does let you keep windows closed on hot days, which helps keep pollen and street dust out.
Types of filter
- Mesh pre-filters: fitted to every unit. They catch dust, hair and larger particles and can be washed and reused.
- Fine particle filters: fitted to some models to capture smaller particles such as PM2.5.
- Deodorising filters: activated carbon or photocatalytic filters that reduce odours.
- Air purification technologies: ionising, plasma and similar systems that manufacturers say break down or neutralise allergens, bacteria and odours.
Filtration technology by brand
The four brands we install each have their own technology on selected models:
| Brand | Technology | What the manufacturer says it does |
|---|---|---|
| Daikin | Flash Streamer (selected models, such as Perfera) | Uses an electron discharge to break down allergens, odours and bacteria captured by the filter |
| Mitsubishi Electric | Plasma Quad Plus (selected models, such as the Zen range) | Captures and neutralises fine particles, allergens, bacteria and viruses |
| Panasonic | nanoe X (Etherea range) | Releases hydroxyl radicals in water particles to inhibit pollutants and odours, and can run without heating or cooling |
| Bosch | Climate range | Washable filters, with additional filtration on higher-specification models |
These claims come from manufacturers’ own laboratory testing. Real-world results depend on the size of the room, how long the unit runs and how well the filters are maintained. Air conditioning is not a medical device, but cleaner, filtered air is more comfortable for many people.
Air conditioning, hay fever and allergies
In summer, keeping windows closed while the air conditioning filters and recirculates your room air can reduce the amount of pollen indoors. To get the benefit, the filters must be kept clean: a clogged filter cannot trap particles effectively and can make the unit smell musty.
How to clean your air conditioning filters
- Switch the unit off with the remote and, if you can, at its isolator.
- Lift the front panel of the indoor unit.
- Slide out the mesh filters.
- Vacuum off the dust, or rinse them in lukewarm water with a little mild detergent.
- Let them dry completely, out of direct sunlight.
- Refit the filters and close the panel.
Clean the mesh filters every two to four weeks when the system is in regular use. Specialist filters have their own schedule in the manufacturer’s manual. Do not run the unit without its filters.
Signs your filters need attention
- A musty or stale smell when the unit starts.
- Weaker airflow from the indoor unit.
- Dust building up around the vents.
- The room taking longer to cool or heat.
- Higher electricity use than usual.
What an annual service covers
Cleaning the filters yourself keeps things ticking over, but an annual service goes further: cleaning the indoor coil and drain, checking the outdoor unit, refrigerant pressures and electrical connections, and making sure the system is running efficiently. Many manufacturers require an annual service to keep their extended warranty valid. Have your air conditioning and boiler serviced at the same time and your boiler service is half price.
Get expert advice for your home
We install air conditioning across Bromley, Beckenham, Orpington, Sevenoaks and the surrounding areas. Get an instant estimate online, or book a free home survey and one of our F-gas certified engineers will recommend the right system for your rooms.
Get your free online estimate Book a free home survey
