CADR for Air Purifiers

What is CADR rating in Air Purfier?

CADR stands for Clean Air Delivery Rate. In the most simplistic explanation of CADR, it is the amount of air cleaned in one hour. This metric is valid for only home/office or sometimes car use air purifiers. Different metrics are required to measure the effectiveness for large ‘Whole House’ or Industrial Air Purifiers.

Originally, the agency that certifies CADR, comes out with 3 ratings. One for tobacco smoke, second for pollen and third for dust, each figure representing the capability of air purifiers to remove respective pollutants in a given amount of time.

The unit of measurement as defined by AHAM is cubic feet per minute. Some manufacturers however also publish the measurement in cubic meter per hour. The conversion is simple. 1 cubic meter = 35.31 cubic feet. Hence if CADR of an air purifier is 200 CADR (cubic feet / minute), then in other metrics the same CADR is 340 cubic meter / hour.

What CADR ratings may not tell?

  • CADR ratings are very broad
  • CADR do not measure odors and VOC’s
  • CADR’s measure the capacity to clean air at full fan speed

So Which CADR should you choose?

Consumer reports recommend CADR ratings of 150 (cubic feet/minute) or more. The range of CADR can be

  • Dust – 10 to 400
  • Tobacco smoke – 10 to 450
  • Pollen – 25 to 450

Higher CADR, the better it is. However, CADR being an important factor, but should not be the sole deciding factor in your evaluation to buy an Air Purifier. Other factors such as Pre-Filters, HEPA, Activated Carbon are an equally (or sometimes more) important.

What CADR figure is right for you?

As a thumb rule, for Indian homes, adopt the “add 40%” rule. So if you are buying an air purifier for 10Ft X 10 Ft room (equals 100 square feet), buy an air purifier for at least 140  CADR (measured in cubic meter / hour). This is based on the standard ceiling height of 10 feet. Even a little more CADR would not harm. This is in direct interpretation from the recommendations given by AHAM.

Air Purifires