CADR Rating Explained

CADR, the Clean Air Delivery Rate, is a metric that was developed as a way of measuring the performance of air purifiers for home. 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. Starting in 2024, there is a new CADR metric called PM2.5 CADR. PM2.5 are particles smaller than 2.5 microns and PM2.5 CADR is roughly an average of the smoke and dust numbers.

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.

EnergyStar CADR Report

 The EPA EnergyStar program uses CADR as the basis for performance. They also factor in the energy usage. This results in an energy efficiency ratio which is the CADR per watt.

EnergyStar Room Air Cleaner Standard 2.0

 The minimum smoke CADR to watt ratio standard. 

From the table above, this means that for a CADR at or above 150, the smoke CADR needs to be at least 2.9 times higher. 

For a CADR rating of 250, this means the power on high needs to be 86 watts or less. That is 250/2.9.

To put this in perspective, a 250 smoke CADR can clean 387.5 sq ft. The formula is 250 CADR x 1.55 = recommended square foot coverage.

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.

FAQs

Summary

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.

Starting in 2024, 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). Oransi is an AHAM member.

This article was written by Peter Mann, the founder of Oransi. He is the Chair of the AHAM Air Cleaning Council. This is the industry group who oversees the AHAM air cleaning test standards including the AC-1 particle CADR.