How we test air purifiers

Performance (70% of overall score)

Our performance test is based on the clean air delivery rate (CADR) industry standard test for air purifiers.

We test models on their highest fan setting to see how quickly and effectively they remove particles of dust, smoke and volatile organic compounds (VOCs) from the air. VOCs are emitted as gases from solids or liquids, including paints, cleaning products, pesticides, building materials, glues, marker pens and even photocopiers.

We test dust removal using fine particles of titanium dioxide. We burn wood chips to test smoke removal, and we use acetone to test VOC removal.

We introduce these pollutants in a controlled way into the test chamber and mix them into the air. First, we measure how fast they naturally dissipate, or decay, in the air. Then we clear the chamber and repeat the test, this time with the air purifier running. We calculate the percentage of particles the air purifier has removed and compare this with the natural decay rate measured earlier. This tells us how quickly and effectively the air purifier is clearing the air.

Dust removal forms 50% of the performance score, smoke forms 40% and VOCs the last 10%.

Ease of use (30% of overall score)

Ease of use is assessed equally on using the controls and the clarity of their labelling, cord storage, the ease of lifting and moving the unit, and the ease of cleaning.

Noise

Noise isn’t part of the overall score, but we record and publish the noise levels on the highest fan setting, so you can get an idea of which models are quietest.