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CADR Rating Explained

CADR, the Clean Air Delivery Rate, is a metric that was developed as a way of measuring the performance of residential air purifiers. The CADR rating 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.  These represent small, medium and large sized particles. Each is measured and assigned it’s own CADR score.


CADR Certified Air Cleaners

The Association of Home Appliance Manufacturers (AHAM) oversees the CADR rating program. As part of this program, air cleaners are randomly selected and independently tested to confirm they continue to meet the performance levels.

Here is a screenshot of the mod and mod jr CADR ratings from the AHAM website.


Benefits Of CADR

The advantage of the CADR rating is that it gives the consumer a way to compare air purifiers that consider both air flow and filter efficiency. In other words, it provides a way to compare performance across products in a consistent way.

The CADR is basically a reflection 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.  Therefore it does not give you a complete picture for how well the air purifier will work in their environment.


Air Filtering Standard

The CADR is the standard in the US and is shown in CFM (cubic feet per minute). In Asia, CADR is in cubic meters per hour (m3/h).

Most air purifier brands show performance in CFM however some show m3/h in North America and this is misleading because the number is inflated.

For example, 235 CFM = 400 m3/h. 

The AHAM CADR standard is used by EnergyStar for air purifier certifications.

EnergyStar looks at the ratio of CADR to watts on high speed. For CADR's 150 and higher this ratio needs to be at least 2.9.

In other words, if the CADR is 290 an air purifier's power consumption needs to be 100 watts or less.

In the coming years, the EnergyStar standard will be a US federal requirement to sell air purifiers in the consumer market.

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.


How CADR is Tested

  • The CADR is measured with the air purifier run on the highest fan speed. If you will not be running the air purifier on a lower 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 drop in performance. To better understand this our suggestion is to find out how much filter media is in the filters. In addition the size of the air filters 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 rating 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.

How To Choose An Air Purifier By Room Size

The key to having clean air in your home is to ensure the filters are of sufficient quality and there is proper air flow. To help you make the right choice we suggest you read our guide on air purifier room size.



How correct and useful are CADR ratings?

The CADR rating is the best way to compare the performance across air purifiers. Essentially, it gives you a number to know how much clean air is produced on the highest fan speed.

Why is CADR important?

It is important if you are concerned with the performance of an air cleaner. It will let you know whether the air purifier is strong enough to clean your living area.  If an air purifier doesn't have enough air flow it won't be effective in cleaning your room.

Do larger air purifiers have better CADR ratings?

In general, the larger the surface area of the filter and the stronger the fan the better the CADR will be. Tower air purifiers tend to have lower CADR's than box shaped air purifiers.

Does the CADR have limitations?

Yes, there are limitations such as the focus on the highest fan speed. If the air purifier is loud and you operate at a lower speed your actual CADR will be lower. It's not uncommon for air purifiers with only 3 or 4 fan speeds to have much lower air flow on the lower fan speeds. In this case the maximum speed CADR does not represent the actual performance.


The AHAM AC-1 CADR rating is a good starting point in comparing air purifiers. This is the portable air purifier industry standard and is used to determine Energy Star certifications. In the coming years, an EnergyStar certification will be a federal requirement.

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:

  • CADR Rating
  • Filters: efficiency, size and amount of filter media
  • Noise level
  • Motor quality
  • Safety – no ozone and uses no technology that could introduce contaminants. Look for air cleaners certified by CARB (California Air Resources Board) that are mechanical to ensure no chance for ozone.

The CADR is managed by AHAM (Association of Home Appliance Manufacturers) and Oransi is an AHAM member.