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What is CADR?

CADR, the Clean Air Delivery Rate is a metric that was developed as a way of measuring the performance of room air purifiers. The CADR reflects the volume of air in CFM (cubic feet per minute) that is cleaned of particles of certain sizes. To measure the effectiveness in removing different particle sizes, three types of particles are tested: smoke, pollen and dust that represent small, medium and large sized particles. Each is measured and assigned it’s own CADR score.

The advantage of the CADR is that it gives the consumer a way to compare air purifiers that consider both air flow and filter efficiency. The CADR is basically a re-flection of the air flow (CFM) times the efficiency of the air filter. So, if an air filter has 200 cfm and 100% efficiency the CADR would be 200. If the air filter has 200 cfm and 75% efficiency the CADR would be 150.

The CADR is a good way to keep from being misled in marketing messages. For example, if a filter has a very high filter efficiency but low air flow the CADR helps to balance the two. We see this commonly from some manufacturers that use particle counters to show the high efficiency of their air purifiers when selling to customers. This method can be very compelling as the shopper sees how well the particles are removed. While this test is valid it does not factor in other important data points such as the air flow and noise level and therefore does not give the customer a complete picture for how well the air purifier will work in their environment.

While we like the CADR, in our opinion there are additional factors that should be considered when comparing air purifiers. To better understand why it helps to know how this test is performed.

  • The CADR is measured with the air purifier run on the highest fan speed. If you will not be running the air purifier on the highest fan speed then the CADR that you will realize will be lower.
  • The CADR is tested with a new, clean filter so it does not reflect the performance of the air purifier over time. A small, thin filter may test well in the CADR test but soon after show a large degradation in performance. To better understand this our suggestion is to find out how much filter media is in the filters and the size of the filters as both will factor into the expected performance over time. A large filter with a lot of filter media will perform much better than a smaller, thinner filter. You may want to watch out if the manufacturer does not provide this information.
  • The CADR does not factor in noise level.
  • The CADR is not a safety test so it does not measure ozone production, motor reliability or energy usage.

In summary, the CADR is a good starting point in comparing air purifiers however to make an informed choice we feel more information is needed. Here is a short list of the areas we recommend you consider when buying an air purifier:

1、CADR

2、Filters: efficiency, size and amount of filter media

3、 Noise level

4、 Motor quality

5、Safety – no ozone and uses no technology that could introduce contaminants

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