Air purifiers are basically fans with filters inside. Air is sucked in and passed through the filters to capture any particles floating in it. Our testers put them in a sealed test room to measure how well they clean the air of dust, smoke and volatile organic compounds (VOCs).
We've only been testing air purifiers for a short period now, but our expert testers know what makes a good one. Our experts also have 20+ years of experience in heat and cooling products, ranging from pedestal fans to split system air conditioners, portable air cons and ceiling fans.
With so many to choose from, what makes us choose one air purifier to test over another? As with most of our product testing, our aim is to test the most popular brands and types on the market, and what you're most likely to see in shops.
- We survey manufacturers to find out about their range of products.
- We check market sales information.
- We check for any member requests to test specific air purifiers.
From this information we put together a final list that goes to our buyers. They then head out to the retailers and purchase each product, just as a normal consumer would. We do this so we can be sure they're the same as any consumer would find them and not 'tweaked' in any way.
Sometimes there is limited available stock for particular products due to unusual conditions; this has sometimes been the case with air purifiers due to high demand in times of bushfire smoke and the COVID-19 pandemic. This means we can only include the models we're able to actually purchase at the time of testing.
How well does each air purifier remove allergens, such as dust, smoke and VOCs from the air?
We test each air purifier with particles of dust, smoke and volatile organic compounds (VOCs) to measure the Clean Air Delivery Rate (CADR) of each machine. This measures the reduction of particles in the air. CADR is an industry standard test for air purifiers and is a good way to compare models, but be aware that performance in your home might be different due to different room sizes and shapes and varying levels of pollutants.
Each unit is tested on its highest fan speed setting.
We calculate the percentage of particles removed by the machines and compare this with the particles that are naturally removed from the air with the machines switched off. The best air purifiers will remove more than 90% of the particles used in our tests. The worst remove significantly fewer.
We test dust removal using fine particles of titanium dioxide. Smoke removal is tested by burning wood chips, and VOC removal is tested with acetone.
Pollen is a common indoor air pollutant and is a typical test for air purifiers, but unfortunately technical difficulties with pollen testing prevented us from measuring performance in this test. We intend to keep trying to find a way to include a pollen test in future. Meanwhile, any model which performs well in dust removal should also be good at removing pollen.
How noisy is the air purifier on high and low power?
One in ten air purifier owners we spoke to told us that their machine affected their sleep. So, we test models on their highest and lowest settings so you'll know which ones are the least likely to disturb you.
We weight each of our criteria a little differently based on the consumer need.
- Dust, smoke and VOC removal, weighted 50/40/10, make up the Performance score.
Ease of use: 30%
- Based on the model's onboard controls, its remote (if it has one), how easy it is to move around, whether it's prone to tip over, how easy it is to clean, and the quality of the supplied instruction manual.