What is a CADR rating? Air Purifier Rating Explained (2022)

The quality of an air purifier is reflected in its maximum airflow and the filtration technology it uses. I have written about filtration several times before, so I will dedicate this blog post to airflow. To connect all air purifier manufacturers and standardize the measurement of the power of one air purifier, AHAM (Association of Home Appliances Manufacturers) has designed the CADR test.

CADR stands for Clean Air Delivery Rate, and this is one of the most important features to look out for when buying an air purifier. Thanks to the CADR rating, we can easily choose the air purifier we need. We can easily check the device’s power, and of course, based on that, we can for sure know in which room to use each air purifier.

What is a CADR rating? Air Purifier Rating Explained

Many air purifiers are not AHAM verified, which means they do not have verified CADR data. Some brands display CADR ratings from third-party laboratories, which are not always 100% accurate. This potential lack of information makes it difficult to compare different air purifiers and decide which is the best buy. However, a decent air purifier and well-known brands are usually AHAM verified and provide CADR ratings. You can find the ratings usually on the air purifier box, so you know what to expect before even opening the box.

In the rest of this article, I will describe what CADR is, how it is calculated, how we benefit from devices with a higher CADR, and whether this measure is really that important.

What is the Clean Air Delivery Rate (CADR)?

According to AHAM, CADR measures a device’s ability to reduce smoke, dust, and pollen particles in a size range of 0.10 to 11 microns (μm) from the air. To simplify even further, let’s say that the CADR is a value that indicates how effectively an air purifier reduces smoke, dust, and pollen. How it can effectively remove 0.9 and 1.0 μm smoke particles, 0.5 and 3 μm dust particles, and 5 and 11 μm pollen particles. This means that the larger the CADR rating of an air purifier, the more efficiently it will clean the air in your home.

We can also say that the CADR is the airflow reflectivity (CMF). Basically, if an air purifier has a CFM of 300 and an efficiency of 100%, its CADR would be 300 (this is just an example). Or if, say, an air purifier has a CFM of 300 and an efficiency of 50%, its CADR would be 150.

Basically, always check that the air purifier is AHAM certified and that the room coverage data presented by the company on the presentation page is correct and corresponds to the AHAM values.

CADR only refers to the air purifier’s efficiency in purifying the air. It does not refer to ozone production, engine trustworthiness, or energy consumption.

How is CADR calculated?

What you need to know about the calculation of the CADR value is that it always shows the value when the air purifier is running at maximum speed. This means that at all other speeds, the CADR is significantly lower.

As I mentioned earlier, AHAM is an independent organization that carries out CADR measurements. CADR is always calculated and tested with a new air purifier with a clean filter that has not been used before. Basically, the CADR is calculated by creating the conditions for which the CADR rating is determined. This requires a room of specific dimensions, a pollutant (maybe a cigarette smoke), an air purifier, and an air quality meter.

Once you have sufficiently polluted the room, measure the current air quality, then re-measure the air quality every few minutes and monitor the progress. Finally, the most important thing is to determine the device’s effectiveness. In other words, how effectively it has cleaned the air in the room for a given period.

Finally, to obtain the CADR, you need to multiply the airflow from the device (CFM) by the efficiency of the test described above. For example, if a device has a CFM of 300 and test efficiency of 50%, the CADR for this device is 150.

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Is a high CADR better?

Of course, it is! If you use an air purifier in a larger room, it is logical that you will need an air purifier with a high CADR.

Is CADR the same as CFM?

CADR is not the same as CFM. However, the two values work together. In fact, CADR is derived from CFM by multiplying CFM by the air purifier’s efficiency.

What is AHAM verified?

AHAM verified means that the air purifier has been tested and certified by AHAM (the Association of Household Appliance Manufacturers) and has a specific CADR. AHAM is an independent organization.

Does the CADR decrease over time?

Basically, yes. The CADR can decrease over time, most commonly due to filter contamination. I, therefore, advise everyone to clean the pre-filter as often as possible, or at least once a month.

Are CADR and airflow the same thing?

They are not! Airflow is a value that shows how much air comes out of the air purifier. While CADR shows how much clean air comes out of the air purifier. The CADR is always less than the airflow.


Finally, I took some time to explain what CADR is, how it is calculated and how important it is when choosing an air purifier. However, remember that you do not necessarily need to buy an air purifier with the highest CADR, especially if you intend to use the unit in a small room. This is because an air purifier with a very high CADR can idle in a very small room, leading to higher energy consumption, unnecessary filter wear and tear, and not necessarily better performance overall.

If I had to summarize in one sentence what CADR is, I would say, “CADR will tell you whether an air purifier is powerful enough to clean the air in your room.”

I would like to remind you to change and clean the filters regularly, especially the pre-filter, as this will always keep the CADR at its highest level. If you have any questions on this topic, I invite you to leave a comment in the comment box below.

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