Is a Higher Air Purifier CADR Better?

Selecting an air purifier for your home might be more challenging than you expect. This is because there are so many ratings and measurements to consider, with CADR (Clean Air Delivery Rate) being one of the standard ones. Given that it measures an air purifier’s filtering performance, is a higher air purifier CADR better?

A higher air purifier CADR is better because the air purifier will clean your room faster. If an air purifier has a high CADR rating, its fan force is substantial enough to cover a larger space. CADR values increase as room sizes increase, so smaller rooms will benefit more from a higher air purifier CADR

This article explores a high CADR rating and whether a higher CADR purifier is better. I also discuss a good CADR rate and the air purifier with the highest CADR.

What Is a High CADR Rating?

The CADR is a standard set by the AHAM (Association of Home Appliance Manufacturers). The AHAM defines CADR rating as the rate at which a running air purifier reduces contaminants in a test chamber, multiplied by the chamber’s volume in cubic feet.

It measures a unit’s effectiveness in removing different-size particles. The sizes are represented by three particle types: smoke (small), pollen (medium), and dust (large). The CADR rating is only for portable air purifiers.

A CADR rating considers the particle size, the percentage removed, and the volume of air passing through the air purifier. The figures you see represent the volume of air in cubic feet per minute (CFM) that’s cleaned of the tested particles.

Suppose an air purifier has a maximum airflow of 300 CFM, and its CADR value is 200 CFM. This means the unit could process 300 CFM, but it’ll clean only 200 CFM effectively in the first cycle. After that, it’ll process the remaining 100 CFM in the next cycle.

The CADR test procedure uses particles ranging from 0.1 to 11 microns in size, and here’s the breakdown:

  • Smoke particles—01 to 0.3 microns
  • Dust particles—0.5 to 3 microns
  • Pollen particles – 5 to 11 microns

The test involves placing an air purifier inside a test chamber representative of a 12 x 12 room with a seven-foot-high ceiling. Dust, tobacco smoke, and pollen pollutants are introduced into the test chamber, and the unit is run (at full speed) for 20 minutes.

Pollen testing ends after ten minutes, and the remaining contaminants are tested at the end of the running time. AHAM calculates a total CADR rating by combining the purifier’s rates to remove the three pollutants from the chamber. Each pollutant’s CADR is also measured, and their value ranges are:

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

A high CADR rating means the air purifier filters the air fast. Therefore, high ratings will be closer to the maximum values possible (400 and 450). If the ratings between any two air purifier brands are similar, they have identical filtering capacities.

Is a Higher CADR Air Purifier Better?

Maximum airflow and filters were the only standards of air purifiers in the 80s. People understood these parameters, but nobody could tell an air purifier’s efficiency at removing indoor air pollutants. With CADR, you can better grasp how efficiently an air purifier eliminates particles.

Since the CADR came on board,  it’s become a key standard to compare air purifiers. It’s a good parameter for checking the quality and efficiency of air purifiers, but there’s more to look consider. While a higher CADR air purifier is good, this feature alone doesn’t make it better than others.

Faster cleaning doesn’t equate to thorough cleaning. CADR only measures the speed at which an air purifier clears specific particulate matter from the air—dust, smoke, and pollen. It says nothing about the purifier’s air quality back into the space (semi-clean or fully clean).

Other parameters, like filtration efficiency, are better suited to determine the thoroughness of an air purifier’s purification process. Therefore, a higher CADR air purifier isn’t necessarily better.

The Limitations of CADR

While CADR is a good comparison standard between air purifier brands or models, it has certain limitations. The CADR test is responsible for most of the restrictions, and I describe them below:

The Test Duration

The CADR test runs for 20 minutes, and it’s a long enough time to judge all air purifiers’ capacity. Some purifiers take at least an hour to circulate air, so rating them at their 20-minute mark is a tad unfair. Air purifiers with a high filtration efficiency take longer to circulate air and get a lower CADR value.

On the flip side, air purifiers with a higher CADR value circulate air faster but remove a smaller volume of pollutants. Also, some devices perform well in those 20 minutes but falter later. CADR tests new filters, and it’s not an indicator of a purifier’s performance over time as it removes contaminants from the air.

The Particles Tested

CADR test doesn’t cover particles smaller than 0.1 microns (ultrafine particles). Unfortunately, over 90% of all particles in the air are ultrafine, and they pose the most significant health risk. These particles could include airborne microorganisms like viruses and bacteria.

You cannot rely on the CADR rating to disclose an air purifier’s efficacy against the most dangerous and numerous particles.

The High-Speed Setting

Air purifiers run at the highest speed during the 20-minute test, but most people don’t run their purifiers at this speed consistently. Due to noise considerations, you’re more likely to choose a lower speed at your home or office. 

The high-speed setting in the test translates to a CADR rating that may not be accurate when you use the air purifier. Changes in speeds can also affect a unit’s filtration capabilities, so testing at high speeds alone is insufficient.

The Bias Against Certain Types of Filters

Air purifiers use various filters to clean and improve indoor air quality, and any standard test should consider this. However, CADR has a bias towards certain filters and, thus, the air purifiers that use them.

Most models that clean the air well but have a lower circulation rate usually have a lower CADR value. This occurs because air purifiers with a greater filtration efficiency can have slow airflow, and CADR measures airflow speed.

Consequently, an air purifier with a HEPA filter may have a lower CADR rating. Even though a HEPA filter can remove 99.07% of particulates larger than 0.3 microns, it doesn’t score well on a CADR. 

The Substances Excluded

Particulate matter isn’t all that contaminates indoor air. Chemicals, odors, and harmful gases also reduce your home’s air quality. When you buy an air purifier, you should be able to tell if it can handle most, if not all, of the pollutants in the air. 

The CADR test doesn’t cover an air purifier’s efficiency against odors, harmful gases, and chemicals. Most AHAM-certified air purifiers don’t reduce odors and gaseous pollutants effectively, if at all. 

What Is a Good CADR Rate?

The AHAM 2/3 rule estimates a good CADR rating for an air purifier. According to the rule, your air purifier’s CADR should equal at least 2/3 of the room’s area (CFM). For example, a 120 square feet room would need an air purifier with a tobacco smoke CADR of at least 80.

With ceilings above eight inches, you’ll need an air purifier that’s CADR-rated for a larger room. If the CADR rating of the purifier you like is less than 2/3 of the maximum airflow, stop liking it.

A good CADR rating should also be at least two times the fan’s highest speed power. This is crucial because running the air purifier at a lower fan speed reduces the fan’s airflow, decreasing the CADR.

Consumer Reports grades CADR from poor to excellent, as follows:

  • Below 60 CFM—Poor 
  • 119 to 60 CFM—Fair 
  • 179 to 120 CFM—Good 
  • 240 to 180 CFM—Very Good
  • Above 240 CFM—Excellent

Any rating above 200 CFM would also be good for an air purifier, as it’d cover 310 square feet.

Which Air Purifier Has The Highest CADR?

A sure way to get an air purifier that will live up to its claims is to choose one with a high CADR. The higher the CADR, the faster it’ll remove the pollutants in the air within your home. The three air purifiers with CADR ratings above 500 CFM are:

  1. Gocheer GH-Monster – 588 CFM
  2. Medify MA-112 v2.0 – 560 CFM
  3. Blueair Classic 605—500 CFM

Of the three, only the Blueair Classic 605 is AHAM verified. Although these models have a high CADR, that’s not the only quality or rating of a good purifier. Other features to look out for before choosing one are:

  1. The amount of filter media and filter size and efficiency.
  2. The noise level of the air purifier.
  3. The safety levels of the purifier—no ozone production.
  4. The motor quality of the air purifier.

The CADR ratings only indicate an air purifier’s cleaning capacity, not its cleaning capability. An air purifier’s purifying technology and filters are better indicators of its cleaning capability. Buying the best air purifier for your needs requires some due diligence, but it’ll be worth every fresh breath you take.