What is a CADR rating?

On our home page and best purifier buying guide we recommend that you consider a purifier’s clean air delivery rate (CADR). The CADR rating is a great way to gauge how effective a purifier is at… well, purifying. The Association of Home Appliance Manufacturers assigns this rating after thorough testing; providing a standard independent of marketing hype.

With that said, CADR is a good standard, but it’s far from perfect. When it comes to higher-end units we advocate looking beyond the rating. Some of our favorite purifier companies opt out of  CADR testing. Companies like Alen, Austin Air, and IQAir opt out of testing often citing its limitations (covered below).  Our recommendation; lean on CADR for purifiers from lesser known companies. For more costly units look beyond the rating and consider other factors before you place an order.


Challenging the CADR System: Alen BreatheSmart

Beyond CADR rating

When it comes to purifiers that do not undergo CADR testing; Alen’s BreatheSmart line is a sure thing. We’d confidently recommend it over almost every CADR tested unit.

See Pricing and Reviews on Amazon.com


The AHAM

So what exactly is the Association of Home Appliance Manufacturers (AHAM)? First, they are the organization that unites reputable manufacturers of household appliances. From ovens, to washing machines, to air purifiers the AHAM helps shape the future of household appliances. Second, they compile and provide research results and sales statistics on almost any home appliance sold globally. Third, they advocate and provide input that shapes public policy focused on home appliances. And, perhaps most importantly the AHAM develops standards of safety and performance for household appliances. Standards like the Clean Air Delivery Rate attached to the best air purifiers available.


What is a CADR rating

Independent third party laboratories Air purifiers test purifiers for the AHAM’s “Verifide” Program. During testing the purifiers are bombarded with three common airborne contaminants; tobacco smoke, dust, and pollen. In a controlled environment the purifier is turned loose  for a short period of time to remove these contaminants from the air. After the test, qualified professionals  measure the concentration of tobacco smoke, pollen, and dust and assign a CADR. In addition to the Clean Air Delivery Rate, the results of the test establish a recommended room size for the purifier.

CADR Rating

Identifying certified purifiers is easy thanks to clear labeling. Image courtesy of AHAM

Beyond that, if a tested device bears an Energy Star Rating, the laboratory will measure energy consumption while the device is in operation. Since the AHAM is approved for official Energy Star verification testing; thier seal of approval is a solid way to ensure you’re making a wise purchase. As a recognized EPA certification body you know that if a purifier was tested (and passed) AHAM certification, you are buying an excellent product.

CADR Label Location

Example of label location. Courtesy of AHAM.


How is CADR calculated for air purifiers?

The test environment and procedure for measuring clean air delivery rate in air purifiers involves the following scientific controls aimed to reduce the impact of variables:

  • Room Size; the purifier is placed in a space that’s volume measures 1,008 cubic feet
  • Pollen Test Duration; The machine is exposed to pollen for 10 Minutes
  • Smoke and Fine Dust Test Duration: The machine operates for 20 minutes each

To further reduce the impact of variables during the test; the particulate size is restricted to the following constraints:

  • Pollen will range in size from 5 microns to as high as 11 microns
  • Fine Dust will measure between 0.5 microns and 3.0 microns
  • Smoke particles measured fall in the .10 to 1.0 micron range

So how how is it all measured? Without going into too much detail the amount of particulate distributed in the 1,008 cubic foot space is measured throughout the test cycle. Testers calculate the reduction in contaminants and assign a numerical rating on a scale of 0-450 (0-400 for smoke).

CADR Limitations

First and foremost, there are a lot of airborne contaminants that are as small as .3 microns. That’s why HEPA filters are designed and rated from their ability to remove particles .3 microns and larger. CADR does not cover particulates in the .3 to .499 microns range. And, that is a lot of contaminants. In fact, most pathogens (bacteria and viruses) are smaller than .5 microns.

Next, Ozone generating machines excel in the test environment. This is a bad thing. Why? Because ozone is a harmful compound unless used in a very narrow range of applications. In fact both the EPA and American Lung Association warn that ozone is both harmful and irritating to respiratory system. Especially the sensitive respiratory system of asthmatics and those suffering from COPD. The takeaway, don’t assume that a purifier is safe just because it has a CADR rating. Make sure that it does not produce ozone. (Note: Ozone  Specs may be Provided to AHAM by Manufacturer)

Finally, many consumers purchase an air purifier to tackle odor, VOCs, and gases. The test environment fails to address any of those contaminants. It’s not an intentional omission by the AHAM or laboratory. It’s just that mechanical filtration methods do not typically address these contaminants. Even the best HEPA filter cannot strip these nasty pollutants from the air. Therefore, removal requires an additional step – adsorption. You’ll need something like activated carbon to address odor, VOCs, and gases. The takeaway; consider a high CADR a bonus when you’re shopping for a purifier to remove these contaminants.

CADR Rating for Dust

If you’re concerned with removing dust from the air, a purifier with a solid CADR rating will serve you well. However, also remember that one of the best ways to fight dust is to remove it before it becomes airborne. You can reduce dust by vacuuming and dusting regularly. And, any dust you miss can be the responsibility of the purifier. And, the higher the CADR the better the purifier will be to keep remaining dust under control.

CADR Rating for Smoke

A high rating will show that a purifier can remove the majority of large particles produced through the combustion of tobacco (or marijuana if that’s your thing). This is essentially the smoke you can see. However, any odor or gas produced will pass through a high CADR filter that isn’t accompanied by an activated carbon filter.

CADR Rating for Pollen

For the most part pollen is huge in size when compared to other airborne contaminants. So, for allergy sufferers a high CADR rating is a great way to tell how well a purifier performs. A high rating will single out a purifier that will diligently strip pollen from the air you breathe. Thus helping keep your seasonal allergies at bay.


Our Favorite CADR rated Air Purifier: Blueair 603

CADR Rating Blue Air 603

The Blueair 603 scores CADR ratings of >400 (Dust); >450 (Pollen); >450 (Tobacco Smoke). It is also Energy Star Certified

See Blueair 603 Pricing and Customer Reviews on Amazon.com


Final Thoughts

Bottom line; use CADR ratings to help make a decision. But, if you’re going to spend over $300 on a room air purifier the majority of our top recommendations aren’t rated. Understanding CADR is beneficial, but don’t use the rating system to rule out a purifier that isn’t rated.

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