Is CADR Important in Air Purifiers?

Selecting an air purifier for your home may feel like the Hunger Games sometimes. All you want is a product that cleans up the air in your home, but there’s a marketing acronym soup to survive. However, CADR is a popular standard amongst the acronyms on your air purifier label, so it must be important, right?

The CADR in air purifiers is essential for checking their efficiency in removing pollutants. While this is a vital rating in air purifiers, I can’t say it’s the most important. However, it does help consumers narrow down their options among the hundreds of “best” air purifiers in the market today.

This article explains what the CADR is about, if it matters in air purifiers and why it’s crucial. I also describe how to calculate CADR for air purifiers.

What Is CADR in Air Purifier?

The CADR is an AHAM (Association of Home Appliance Manufacturers) standard for air purifiers. According to the AHAM, it’s the rate at which a running air purifier reduces pollutants in a test chamber, multiplied by the chamber’s volume in cubic feet. The measurement also excludes the rate of natural decay of the contaminants when the air purifier isn’t running.

In simpler terms, CADR indicates the volume of clean air the purifier releases on the highest fan speed. For example, if a filter removes 80% of particulate matter (efficiency) and the air purifier produces 100 CFM, the CADR will be 80.

CADR measures a unit’s effectiveness in removing different-size particles. Three particle types represent the sizes: smoke (small), pollen (medium), and dust (large). The CADR rating is only for residential portable air purifiers, and it can’t apply to whole-house air purifier units.

A CADR rating considers the particle size, the percentage of particles 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. The unit of measurement in Europe and Asia is cubic meters per hour.

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.

How to Measure CADR

The AHAM conducts the test independently with randomly selected products to ensure that the products maintain the correct performance levels. In addition, the AHAM uses a test method the American National Standards Institute (ANSI) recognizes to avoid questions about CADR validity.

The ANSI recognizes the method as an American National Standard, and it’s also used in the US Environmental Protection Agency (USEPA) Air Cleaner Energy Star Program.

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

  • Smoke particles—0.1 to 0.3 microns (ultra-fine particles)
  • 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 they run the unit (at full speed) for 20 minutes.

Pollen testing ends after ten minutes, and they test the remaining contaminants 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

Since the test only measures the CADR at the highest fan speed, running it at lower speeds will reduce the CADR. Although the CADR test has high validity for most residential purifiers, the testing chamber volume sets some limitations.

The chamber volume limitations don’t matter for residential air purifiers, but it does when testing for CADR in industrial units. This limitation manifests as maximum CADR ratings for the primary particles tested, as shown below:

  • Maximum dust CADR rating—400 CFM
  • Maximum pollen CADR rating—450 CFM
  • Maximum smoke CADR rating—450 CFM

The higher the CADR rating, the faster the device filters the air. High ratings will be closer to the maximum values possible (400 and 450). Two air purifier brands are similar, with identical filtering capacities, if their CADR ratings are the same.

Does CADR Matter in Air Purifiers?

Before the CADR standard came on the scene in the 80s, filters capacity and maximum airflow were all that people used to grade air purifiers. They were and still are excellent parameters, but that’s not all you need to know before choosing an air purifier.

Thanks to CADR, you can get a well-rounded picture of an air purifier’s capacity before opening your wallet. Of course, it’s better to know what you’re going in for before a hidden or missing feature in your device surprises you.

An air purifier’s CADR tells you how it will work in rooms of a specific size. Air purifiers with a higher CADR rating are meant for larger rooms. This means if you buy one of such for a smaller space, it’ll clean the room’s air faster.

Seeing how valid it is, you should understand how to read and interpret the CADR values you see. Here are some guidelines to help interpret CADR ratings:

  1. The AHAM seal—often on the back of an air purifier’s box—will have three numbers. Each number represents values for dust, pollen, and tobacco smoke.
  2. Next, check the suggested room size for the device.
  3. Refer to the CADR numbers for the particles to see how fast the unit will filter each one regarding the recommended room size.

If you’re comparing two air purifiers, these are details to note. First, ensure you purchase an air purifier that’s powerful enough to tackle the size of the room you have in mind.

Why Is CADR Important?

There are three significant benefits of CADR, and I describe them below:

Product comparison: It bears repeating that consumers wouldn’t be able to compare air purifiers that consider filter efficiency and airflow without this standard. Suppose product A had an airflow value of 200 CFM and 75% efficiency, and product B has 200 CFM with 100% efficiency. 

The CADR for product A would be 150, and that of product B would be 200. With this information, you can select product B over product A without being torn about the similar airflow (CFM).

Seeing through marketing messages: Although many air purifiers have truthful information on their packaging, some have marketing messages that may be misleading. For example, if a cleaner’s filter has a low airflow but an extremely high filter efficiency, the CADR helps bridge the gap.

Some manufacturers use high particle counters to convince customers of the product’s high efficiency. However, while it’s a valid test/parameter, it doesn’t factor in airflow, which CADR measures.

Finding a product that meets a specific need: Air purifiers carry a total CADR rating and the three particles’ CADR ratings. This can help you select an air purifier that’ll most effectively handle your specific air quality issue.

If you have an issue with pollen (over dust or tobacco smoke), you can choose a unit with a higher CADR rating for pollen. You can ensure that the air purifier selected will rapidly and efficiently rid your indoor air of pollen.

Of note, you can’t find high CADR ratings for all three particle ranges. The different airflow requirements make this impossible. For example, if an air purifier gets high CADR values for pollen and dust, it may not be as efficient in removing tobacco smoke particles.

CADR gives you an objective standard for evaluating an air purifier’s efficiency and speed. 

How Do You Calculate CADR for Air Purifiers?

As you shop for the perfect air purifier for your home, you will make some shocking discoveries. One of which is that many air purifier manufacturers don’t test their products with the AHAM. Such air purifiers only provide the maximum airflow (in CFM) on the specification page.

Regardless of this lack of information, you can estimate the CADR from the maximum airflow value provided. This is a suitable alternative because you might not have the capacity to recreate the standard AHAM CADR test (facility and conditions).

The AHAM has a simple 2/3 rule for this purpose. The rule states that your air cleaner’s CADR should be equal to at least two-thirds of the room’s area. Here’s an example of how it works:

If the maximum airflow is 200 CFM and you apply the 2/3 rule, your CADR would be 2/3 of 200 CFM. Therefore, the CADR rating would be around 133 CFM.

You can also derive an appropriate CADR for your room size by dividing the room’s square footage by 1.55. For example, suppose your room is 300 sq. ft. Dividing it by 1.55 gives a CADR of 194, so you should get an air purifier with a CADR of 194 and above.

AHAM recommends picking an air purifier with a tobacco smoke CADR rating that’s at least 2/3 of the selected room’s square footage. Tobacco smoke particles are the most difficult to filter out of the three particles tested, so they’re an ideal standard. 

An air purifier with a high tobacco smoke CADR rating will also filter larger pollutant particles efficiently.