What is CADR in Air Purifier?

The most common method to measure the effectiveness of air purifiers is the CADR rating. CADR is abbreviated for clean air delivery rate. It is a common specification that determines the strength of electronic devices. But most of the people are unaware of what is a CADR rating.

It was developed as a method to measure the performance of specifically residential air purifiers. This rating shows the volume of air cleans in cubic feet per minute of particular sizes that get cleaned.

The effectiveness of this process is done by testing and removing three particles of different sizes. The three particles that are tested are smoke, dust, and pollen.

In this article, we have talked and explained what is CADR rating in a purifier and everything related to it. After you go through this article your doubt regarding CADR will clear and you will be able to confidently explain everything related with it.

What is CADR Rating?

CADR is the full form of clean air delivery rate. In general, it is a numeric value that reflects how much particles are removed by your air purifier. In layman’s terms, it tells you how fast your air purifier can purify the air of a room of a particular size.

Measurement of CADR rating is measured in CFM or cubic feet per minute. It can also be measured in cubic meters per hour. This rating is usually done for dust, pollen, and smoke. These are unwanted pollutants in the air and are very small in size.

These particles are invented by the Association of Home Appliance Manufacturers or AHAM. You can say that the CADR rating by AHAM is the most accurate. The air purifier fan is more powerful if its CADR rating is better. High CADR rating means the fan power of the air purifier can cover a larger room.Size of smoke particles varies from 0.1 to 0.3 microns making them ultra-fine. One of the common particles that you will find in air are dust particles. Its size ranges from 0.5 to 3 microns. Pollen particles are considered to be large particles. You can see these particles with your eyes as their size is between 5 to 11 microns.

Who Calculates CADR Rating

CADR tests are usually conducted by the Association of Home Appliance Manufacturers. AHAM tests the quality of the air purifiers. The manufacturers submit their air purifiers voluntarily to AHAM. Once the manufacturers submit the air purifiers, AHAM conducts the testings. For every air purifier, the same test is conducted by AHAM. This makes the CADR rating consistent and shows a good measure for the efficiency of air purifiers.

How is Air Purifier CADR Rating Measured

The CADR rating is measured by the ANSI/AHAM AC-1 test. You can easily understand this test and the test result is very accurate.

The steps involved for the CADR testing are as follows:

  • The testing purifier is put inside a chamber by the agency. The chamber consists of the different amount of contaminants that is desired.
  • The purifier is run for around 20 minutes and then it is stopped.
  • After stopping the air purifier, the chamber’s air is measured once again.
  • After taking the measurements before and after, the CADR rating is determined for that particular air purifier.

But the test also has some limitations. The limitations are:

  • CADR rating is for only the three specific contaminants. If you wish to measure for bacteria or virus the CADR rating by AHAM is useless.
  • Also, the test is short as the limit for testing is maximum 20 minutes. Several air purifiers work efficiently for the starting 20 minutes but fail to work efficiently afterwards.
  • The CADR rating can be false because of the ionizers. In the process of ionization, small particles stick together to form one large particle. The bigger particle does not get trapped. Instead, this particle drops on the floor or hits the walls. Thus, the particles are not removed properly, and get ready to be free in the air again.

We understand that CADR rating is a crucial factor to choose the right air purifier but has limitations. We need to keep these limitations in mind and look through other factors as well. You should choose an expensive air purifier over a cheap one even if the CADR rating is low. This is because the quality of filtration is much better for the expensive one.

What is a Good CADR Rating for Air Purifier? (AHAM’S ⅔ rule)

After you understand what is CADR and its importance, you will want to look through different air purifiers. You would like to know the CADR rating of all the purifiers that you are considering to buy.

But the sad reality is not all the manufacturers conduct AHAM CADR rating tests. The purifiers that do not conduct these tests, come with only maximum airflow rating in CFM.

The question arises, how do you calculate the CADR rating from the maximum airflow? 

The simple answer to this question is you can’t find the rating from the maximum flow of air. This is because CADR rating is measured inside a chamber and not calculated. But, now AHAM has introduced a simple rule. The rule known as AHAM’s ⅔ rule helps you estimate CADR rating based on the maximum flow of air.

To understand how this rule works, let’s take an example.

Consider going through a specification sheet of an air purifier. In the specification sheet, you notice that maximum airflow reads 200 CFM. you are unable to find any details regarding the CADR rating. According to the rule, you can find out the CADR rating by multiplying maximum airflow with ⅔ . Thus for maximum airflow of 200 CFM, the CADR rating will be around 133 CFM.

What is ACH? Is ACH Related to CADR Rating?

The full form of ACH is Air Changes per Hour. The ACH rating specifies exactly how many times the air purifier exchanges air in the room per hour. Better quality of air can be understood by the exchange of more fresh air.

Along with the CADR rating, ACH rating specifies the power of the fan present inside the purifier. This means an air purifier having higher ACH rating will perform and clean better than a lower ACH rating air purifier.

Final Word

If you are starting to look for air purifiers, and want to compare among different purifiers CADR rating is a good start. After going through this article, we hope that all your doubts related to CADR rating as well as clean air in air purifiers is clear. We have given a detailed description about every aspect we thought is related to CADR rating. If you are confused about the CADR rating, feel free to write to us and we will be happy to help you.