What is CADR in Air Purifier?

CADR in an air purifier is a technical specification that represents how efficient or how much air is filtered in certain period of time.

If you want to know more about what CADR is, how and why it matters, then this article is for you.

We have mentioned all the information required for you to understand it and analyse this factor while purchasing the air purifier.

What Is CADR Rating?

CADR is generally a numerical value that shows the volume of the air purified. It displays the number of pollutants to be removed from the air.

CADR measurement is essentially for three crucial pollutants in the air. They are – pollen, dust, and smoke. These are very small in size and most unwanted particles that contaminate the air. 

The CADR rating measures for each category. It shows how effectively the air purifier could remove the particles from how many cubic feet of air every minute.

Here the highest scores or ratings for all three particles. For smoke and pollen, the rating is 450, whereas for dust, 400. Remember, the highest CADR rating shows the efficiency of the air purifiers in removing pollutants from the air.

You measure CADR in cubic feet per minute (CFM) or m³/hour. Whenever you are purchasing an air purifier, look for this rating.

You can compare the CADR numbers of each air cleaner in the market, and then choose the unit accordingly. This rating helps the user in determining the most suitable unit for his or her room.

Click here To Know air purifier vs humidifier

Who Calculates CADR Rating?

Let us learn about who calculates the CADR rating. AHAM or Association of Home Appliance Manufacturers is an organization that is responsible for calculating the CADR rating. AHAM conducts the CADR tests and evaluates the quality of the air purifiers. This is how it goes:

The manufacturers submit their air purifiers to the AHAM.

After submitting, the AHAM tests these devices.

The test is the same for every air purifier submitted by the manufacturers.

Because of this test, the CADR rating remains consistent and shows the exact measurements for the efficiency of each air purifier submitted.

How Do You Measure CADR Ratings?

This is how you can measure the CADR rating. As per the ANSI/AHAM AC-1-2006 directive, the AHAM conducts all CADR testing in a 1008 ft3 test chamber. This chamber is nothing but a room with having a dimension of 12×12 feet and a seven feet high ceiling.

Let us get into the process:

  • As the initial step, they place the air purifier in the test chamber to conduct the CADR testing.
  • They leave the device inside for about 20 minutes.
  • After 20 minutes, they draw the results of the three particles.
  • Now, they measure these results against the pre-test levels.
  • After that process, the CADR seal suggests the appropriate room size for the air cleaner. It calculates this by using a specific formula based on the test results.
  • As per the room size, the CADR gives three different metrics. These values reveal how efficient the air purifier is in removing the contaminants from the room within those 20 minutes.
  • The three different metrics include Smoke CADR, Dust CADR, and the Pollen CADR rating.
  • The higher the number is, the larger amount of air gets filtered in that particle size range.
  • The AHAM separates the three pollutants and makes three different CADRs for each one. Thereby, it helps the consumers to decide between the different air purifying units available in the market.

Let us say an air purifier has one contaminant rate as high. Assume the pollen rate is high. If a consumer having pollen allergies tries to purchase a unit, he would prefer this air purifier with a high pollen rating. This would make it easier for the consumers to choose the right device for their home. 

Similarly, a person can choose an air purifier with high smoke CADR rating, if any of his family members smoke cigarettes. This could be a perfect choice for his or her needs.

The AHAM not only measures the CADR rating but also calculates the room size adequate for that air purifier. This evaluated measurement comes printed on the seal to help the consumers choose thoughtfully.

How do they give the room size rating for each purifier? This is how they do. They measure the purifier’s ability in eliminating at least 80% of the smoke particles in a room.

What is a Good CADR Rating?

The good or ideal figure for CADR rating is nothing but the value that equals at least two-thirds area of the room.

Let me give you an example for a better understanding.

Let us say the room has the measurements as 10 feet x 15 feet. The area of that room is 150 square feet. A good CADR rating for an air purifier suitable for this room size would be a smoke CADR of at least 100.

Is Higher CADR a Better Rating for an Air Purifier?

Having a higher CADR rating for an air purifier is not only better but highly preferable. This is because the higher test numbers are an indication that the air purifier is very efficient in cleaning indoor air.

Let us consider an air purifier having high dust CADR rating of 300. Let us take another unit having a low dust CADR rating of 200. If you examine both, the former has high efficiency in reducing the dust particles in the room at a faster rate than the latter.

AHAM states that when you use an air purifier with a higher CADR will clean the air in the room faster and more often. Using an air cleaner is a must for larger rooms whose ceiling is more than eight feet high.

How does CADR play an Effective Role in Comparing between the Products?

The CADR rating has higher significance when it comes to the comparison of products. Let us look at essential steps when comparing.

Firstly, compare the values on the seals and check if the numbers are suitable for your room size.

As the second step, check out the contaminant’s ratings, i.e., the smoke, pollen, and tobacco CADR numbers.

If the particle’s ratings are high, it means they can facilitate a quicker filtration process. If the numbers are the same for the different units, that means all have the same air filtering performance.

However, getting high CADR numbers for all three contaminants is nearly impossible. This is because the airflow requirements may differ for each unit.

Here is an example:

Consider an air purifier that has high smoke CADR rating since it uses a slow fan. Now, the CADR numbers of dust and pollen for the same unit will be lower. The reason is that the pollen and dust particles are larger in size than the smoke. Hence, they will fall down and get deposited in the room itself before the cleaner can collect them during the 20-minute test.

The converse is also true. Let us assume the air purifier has high CADR numbers for pollen and dust. In such a case, it may not be that efficient in removing the smoke particles from the air.

What are the Limitations of CADR Testing?

There are a few drawbacks to CADR testing. Let us learn what they are:

  • CADR ratings are specially designated values or numbers for only specific contaminants like dust, pollen, and smoke. If you need an air purifier for other pollutants like a few kinds of viruses or bacteria, then the CADR from the AHAM is of no use.
  • The other major limitation is the short test of 20 minutes. In some cases, a few units work well within this short period. However, after this time, they tend to decline in their performance.
  • This is one of the significant downsides of CADR testing. It tests the air purifier, only on its highest settings. Most times, people would not turn on the highest setting when sleeping because of the noise concerns. In such a case, the air purifier you purchased for your room, may not be effectively performing as it did during the CADR test.
  • The ionizer is another potential reason that makes the CADR ratings not reliable. During the ionization process, it only gathers all the smaller particles to form a bigger one. It does not trap them. As a result, these bigger particles get dropped on the floor and other surfaces of the room. Since they get deposited and do not get removed properly, there are chances for these particles to get into the air again.

These are some of the drawbacks of CADR testing. However, one should always remember that this rating is one of the factors to choose the right air purifier. There are other parameters and specifications an individual should consider at the time of purchase.

What Is the Significance Of ACH Rating?

ACH is the acronym for Air Changes per Hour. The ACH rating is yet another indicator that shows how many times for every hour the air purifier device exchanges the air within the room. When there is more exchange of fresh air, it means the air quality is better.

Together with the CADR ratings, the ACH rating shows how powerful the air purifier fan is. In other words, an air purifier with 5X ACH can clean a room more times when compared to a 2X ACH air purifier.

If you want to calculate the suitable room size for an air purifier, you need to know the ACH and CADR ratings.

If your air purifier has an average CADR of 300 cfm, it can operate as high as 5X ACH. 

Here is the calculation for the cleaning capacity of the air purifier for one hour (60 minutes):

Capacity = 300 x 60 = 18000 cfm.

Let us assume the room has a ceiling of eight feet high:

18000 (cfm) / 8 (f) = 2250 (f².h)

When you divide this value by the ACH, you will get the rating for ACH: 

2250 (f².h) / 5 (h) = 450 f².

Frequently Asked Questions:

1. Do all air purifiers have a CADR rating?

Ans: Most air purifiers will have the CADR measurement done. However, the rating calculation process done by the AHAM is entirely voluntary. As a result, there will be some purifier manufacturers who will not get the tests done. This does not necessarily mean that these units are less superior or not at par with air purifiers. It just makes it more difficult for the consumers to evaluate which device they should choose.

2. Do larger air purifiers have better CADR ratings?

Ans: Well, the answer to this question is yes. Generally, when the air purifier filter has a larger surface area, and a stronger fan, the better the CADR ratings will be. Tower air purifiers seem to have lower CADR numbers when compared to box-shaped air purifiers.


I hope this article cleared the air on CADR in the air purifier and its significance. The CADR rating is one of the determining factors when purchasing an air purifier. Are you planning to buy a unit? Make sure you compare the CADR ratings of all the devices and then evaluate the product that is most suitable for your needs and home. Let us know your choice by posting them in the comments.

Write to us in the comments section below if you find this article insightful. Let us know if you have any questions or need more information on CADR. We would be ready to help you.

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Stay healthy and stay safe!!!

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