What is the CADR
Rating of an Air Purifier?

Given the vast variety of air purifiers available today, we need some way of comparing the effectiveness of each air purifier in terms of how well it cleans contaminants and pollutants from the air. We could compare in terms of price or additional features such as a timer or night mode, but this does not necessarily give us a true indication of performance.

Price and additional features are a useful tool when choosing the best air purifier. However they should not be reviewed in isolation. They need to be reviewed alongside the CADR rating for a true indication to performance.

The clean air delivery rate or CADR is a benchmark given to air purifiers after undergoing specific independent tests. Put simply, the air purifier is placed in a testing chamber which measures 28.5m3 ¹ (this is considered a standard size room) whilst the air quality is monitored.

Before the air purifier is switched on, the number of contaminants and pollution in the air are recorded. The air purifier is then switched on for a period of 20 minutes whilst the contaminants and pollution are monitored². The total quantity of indoor pollution is calculated at the end of the test which allows the tester to determine how much pollution has been removed from the air. 

For example, an air purifier has been tested and has been given a rating of 100m3/hour. This means that the air purifier cleans a volume of 100m3 of air per hour, or that 100m3 of clean air is added to the room every hour.

The same tests are applied to every air purifier therefore creating a level playing field. This gives the us a vital tool when choosing the best air purifier for our requirements.

As a general rule, a higher CADR is best. However, there is often a price increase to consider and additional features which may be included. We should look at the picture as a whole to determine the best air purifier for the required application. 

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¹ Wikipedia – Clean Air Delivery Rate – https://en.wikipedia.org/wiki/Clean_Air_Delivery_Rate – 2016 

² R. J. Shaughnessy1 and R. G. Sextro2 (2006) – What Is an Effective Portable Air Cleaning Device? A Review – Journal of Occupational and Environmental Hygiene, 3: 169–181