I’ve seen the term CADR on lots of different purifiers. What is CADR?
CADR stands for Clean Air Delivery Rate and it is the metric generated by old test methods dating back to the 1980s.
The CADR metric is a measurement of the clean air volume that a purifier can provide in a fixed amount of time – ultimately a measurement of speed. It measures the amount of filtered air passed through a purifier – but we believe it shouldn’t be a standalone metric to assess the full performance of modern day intelligent purifier.
How does the test work?
The different test standards across the world for generating a CADR metric follow similar stipulations in how the test runs, and the chamber in which it should take place.
The test chamber is small, between 28m3 and 30m3, depending on the methodology. It is a climate-controlled chamber, with solid walls, floor and ceiling. In the centre sits the purifier in question, and particle pollution is injected into the room from the outside through an aperture. A single sensor is installed in one side of the room to monitor the particle count in the room. There are also two fans – one wall-mounted and one ceiling fan – to aid air circulation. At Dyson, we don’t believe this is a representative space for measuring the performance of a purifier in modern homes.
Before the test begins, the purifier is placed in the centre of the room, manually switched on in maximum mode and ceiling and wall fans switched on. A controlled amount of pollutant is pumped into the room, the fans mixing and homogenising the pollutant concentration. At the start of the test, the ceiling fan is turned off, but the circulating fan remains running for the full test. It is conducted with dust, pollen and tobacco smoke, and runs for 20 minutes each time.