What Is A CADR Rating- Air Purifier Rating Explained

If you’re in the market looking for an air purifier, you’ll come across various data metrics illustrating a given air purifier’s efficiency and efficacy. One such data metric that you’ll see often is an air purifier’s CADR rating. But what is a CADR rating, and do you need to consider it before you buy one?

In brief, the CADR rating of an air purifier indicates its effectiveness in removing contaminants from the air.

Although it may get a little tricky to understand, you can select the best air purifier for your space by comparing the CADR ratings of various air purifiers.

In this article, we’ll discuss more on air purifier CADR ratings and how they can assist you in your hunt for an air purifier.

What Is a CADR Rating?

The term CADR is an abbreviation for Clean Air Delivery Rate. The ratings are assigned to air purifiers after examination by the AHAM.

Generally, CADR ratings quantify the removal of 3 contaminants from the air; smoke, dust, and pollen.

When shopping for air purifiers, it is crucial to consider their CADR ratings. It can help you choose the most appropriate model for your space.

An air purifier with a higher CADR rating will cleanse air faster than an air purifier with a lower CADR rating.

While an air purifier has an overall CADR rating, it also has individual ratings for pollen, smoke, and dust. These metrics can be useful if you have specific needs.

Keep in mind that the CADR rating of an air purifier is calculated when the brand-new machine is running at its highest fan speed setting.

However, over time with use, the effectiveness of an air purifier may decrease, leading to a lower CADR.

Before CADR ratings came around, air purifiers were compared by their maximum airflow ratings (CFM). But the CFM rating of an air purifier only indicates how much air it can process in a minute, whereas its CADR rating indicates how much air is purified in a minute.

How Is CADR Calculated?

The standardized method used to test air purifiers’ CADR rating is designed by AHAM.

With a long history and recognition by reputed organizations such as EPA, FTC, and Consumers Union, CADR ratings offer a valid way to know if an air purifier is productive enough.

Air purifiers are tested inside a chamber with a fixed volume of 1008 cubic feet, i.e., a 12×12 ft. room with a 7 ft. ceiling height.

Sensors and other monitoring devices are placed first inside the chamber to measure the number of contaminants (smoke, pollen, dust) in the space.

After the air purifier is placed inside, it is run at full speed/highest setting until all the contaminants are removed from the space.

The CADR rating is then calculated based on the time taken by the air purifier to cleanse the air.

CADR ratings are calculated the same way for portable air purifiers, regardless of their purification methods and technologies. However, whole-house air purifiers rely on other types of testing methods.

What CADR Rating Do I Need?

The CADR rating scale goes up to 400 for dust and 450 for pollen and smoke.

You may be intrigued to purchase an air purifier boasting the highest CADR rating, but you probably won’t need it for your space.

Instead, you should determine the approximate CADR rating you will need based on the total area of the room.

According to AHAM, the CADR of an air purifier should be equal to, or more than, at least ⅔ of the room’s total area.

For instance, a 16 ft. by 12 ft. room has (a 16×12) 192 sq. ft. total area. ⅔ of 192 is 128, so for this room, you’ll require an air purifier with at least a 128 CADR rating.

Most experts recommend getting an air purifier with at least a 150 CADR rating or higher. Highly effective air purifiers have ratings above 350, but anything below a 100 CADR rating won’t perform very well.

However, not all air purifier manufacturers conduct CADR tests – for their air purifiers, the spec sheets will only inform you of the maximum airflow and nothing about CADR ratings.

In such cases, we can conform to another ⅔ rule introduced by AHAM – it states that the CADR rating of an air purifier is about ⅔ of its maximum airflow.

For example, if an air purifier’s spec sheet states that its maximum airflow is 200 CFM, you can roughly estimate its CADR rating, i.e., ⅔ of 200 is around 133. Therefore, the estimated CADR rating of the air purifier should be around 134.

You could use a CADR Calculator, but here’s a table so you can save time –

Size of Room (sq. ft.)Minimum CADR Required (CFM)
300 200
500 334

Limitations of CADR Ratings

Although CADR ratings offer an easy means to compare air purifiers, these ratings don’t often provide the full picture. Here are some of the limitations of CADR ratings-

  • CADR ratings do not factor in noise level – when buying an air purifier, the level of noise should be considered as some models get pretty loud
  • The CADR rating of an air purifier is calculated with its highest fan speed – if you aren’t running the machine at full power, the actual CADR will be lower
  • When the CADR rating is calculated, the filter and components inside an air purifier are brand new. However, the CADR rating substantially decreases with the use
  • Gasses aren’t measured in CADR ratings – there may be hazardous gasses, such as VOCs, ozone, etc., that go unaccounted for in CADR testing
  • CADR ratings don’t indicate the effectiveness of eliminating odors

Why CADR Ratings Can Be Misleading

Although CADR ratings can help in choosing the best air purifier for your space, they could be misleading.

This is because CADR ratings are biased toward models that circulate semi-clean air faster rather than models that purify the air entirely.

Higher filtration can decrease an air purifier’s airflow, while an air purifier with lower filtration efficiency has a faster rate of air circulation. This will lead to the air purifier with lower filtration efficiency having a higher CADR rating.

It happens because, in CADR testing, the air purifiers are run for 20 minutes, after which the air quality is checked, and the CADR rating is calculated.

On the other hand, many air purifier manufacturers designed their models to circulate more air faster by filtering large particles only. These companies often don’t have any other filtration technology apart from HEPA.

However, if you’re thinking of removing pet hair from air with an air purifier, it must have a HEPA filter for effective filtration of animal dander.

Adding better filtration options, such as silver-ion technology and carbon-activated filters, will reduce the CADR rating, making an air purifier less competitive. This is a key reason why some of the top air purifier manufacturers don’t have CADR ratings.

Frequently Asked Questions

1.    What is a good CADR rate for an air purifier?

Experts suggest getting an air purifier that has at least a 150 CADR rating or more. Typically, highly effective air purifiers come with CADR ratings above 350.

On the other hand, air purifiers with less than 100 CADR ratings won’t prove to be useful in most scenarios.

2.     Is a higher CADR rating better?

Although a higher CADR rating means faster removal of contaminants from the air, you probably may not require that much power. Instead, you should consider the size of your room to determine the appropriate CADR rating.

3.     Does CADR matter in air purifiers?

Yes, the CADR rating is important to consider when buying an air purifier. You can compare multiple air purifiers by their CADR ratings and choose the most appropriate model for your space.

4.     How do you read CADR ratings?

Usually, CADR ratings are included in the specs sheet of an air purifier. Besides an overall rating, you may also get an individual rating for each of the 3 contaminants (dust, smoke, pollen).

But keep in mind that a decent air purifier will have at least a 150 CADR rating.

5.     CADR rating for COVID?

There isn’t a specific recommendation for CADR rating for COVID, but it is advisable to get an air purifier that offers the highest individual CADR rating for smoke.

As smoke particles are tinier than dust and pollen, an air purifier with a higher CADR rating for smoke will be the most effective.

6.    What should I look for in an air purifier?

If you have specific needs, such as removing pet hair from air, you’ll need an air purifier that’s good at filtering out those contaminants.

Before selecting one, compare its CADR rating with other models to see which air purifier would be the most effective for your needs.

7.    What is a good CADR rating for dust?

Generally, a CADR rating of at least 150 is recommended by experts. However, if you have dust allergy or related issues, you can look for models with higher CADR ratings (around 300 CFM), as they will be more effective in cleaning the air.

Final Verdict

With all of that being said, we now know what a CADR rating indicates. It is the effectiveness of an air purifier in removing contaminants from the air.

However, the CADR rating of an air purifier won’t inform you if the unit removes odor or gasses.

So, choosing an air purifier based on the highest CADR rating may not be enough if you have health complications. Instead, the CADR rating is more helpful when comparing several air purifiers.


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Billy J. Weber

Hi. It’s Weber, founder and author of this site Currently you are reading. I am dedicated to provide valuable insights and practical tips to air enthusiasts and anyone interested in improving their indoor air quality.

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