So, you’ve decided to buy an air purifier. Maybe you have a child with allergies or you’re worried about the flu or just overall poor air quality.  Whatever the reason, you want to make sure to get the air purifier that works best for you and your family’s needs. One of the best ways to compare air purifiers is by looking at their CADR scores.

What the heck is CADR?

CADR is a rating system designed by The Association of Home Appliance Manufacturers (AHAM) as a way to measure the performance of residential air purifiers. It gives a standard that helps keep consumers from being deceived by misleading marketing campaigns.

While CADR is the standard most often used in the United States.  There are other international standards such as GB:T and EN1822 which are also important to consider.

What does CADR measure?

CADR measures how much air is filtered in an hour for a particular pollutant. For instance, if you were particularly concerned about pollen, you could compare the CADR for pollen on various air purifiers.

The number you see represents how much volume of air is actually cleaned within an hour from pollen pollutants.

What kind of particles does CADR test?

CADR tests how effectively purifiers can remove smoke, pollen, and dust. AHAM defines smoke particles as small, pollen as medium, and dust as large.

Asian tests have been even more thorough, going so far as to test volatile organic compounds, which are tiny gaseous molecules, like formaldehyde.

What is a “good” CADR score?

The higher the CADR number, the faster the air purifier filters the air. However, making your choice purely based on the highest number could leave you with a cleaner that is far too large for the given space, wasting energy and money.

You want to choose a CADR that will match the room size you’re planning to purify. A good rule of thumb is to choose a CADR number that represents at least 3 times the total volume of your room.

So, for example, consider a room that is 200sqft  with 8ft high ceilings. To find the minimum CADR, you would first determine the volume of the room (200sqft x 8ft=1600 cubic feet). Using the 3x rule of thumb, you would then multiply the volume of the room by 3 (1600 cubic feet x 3= 4800 cubic feet per hour). To translate cubic feet per hour, divide by 60 (4800cfph/60 =80 cfpm). So, the minimum CADR for a given pollutant in that room would be 80.

Another way to determine the ideal CADR is to follow AHAM’s 2/3 Rule which says that generally, the CADR of your air cleaner should be equal to at least two-thirds of the room’s area.

For example, a room that is 10 feet by 12 feet has an area of 120 square feet. ⅔ of 120 is 80, so an air cleaner for that room would ideally have a smoke CADR of at least 80.

Are there limitations to CADR?

Yes. While CADR is a helpful measure of an air purifier’s efficiency, it isn’t perfect. There are several drawbacks that need to be taken into account to give a more complete picture.

CADR is evaluated by testing in a confined room, that is no bigger than 400 square feet.

Testing in a small room does not give an accurate assessment of larger rooms, where some of the air purifier models would not be able to reach every corner due to their low airspeed at the outtake of the machine.

CADR does not show the air purifier’s performance over time.

CADR is usually evaluated for mint condition filters and not valid for the entire lifetime of the machine.

CADR does not measure ozone: The effects of ozone can be just as dangerous as poor air quality.

Look for an air purifier that doesn’t use ozone.

CADR doesn’t measure gas.

Gas pollutants can be very dangerous and a purifier’s effectiveness at reducing gas is completely unrelated to how well it reduces particles. AHAM has not yet found a way to test how effective purifiers are at removing gas. There have, however, been some advances recently in European and Asian standards to test air purifiers for removal of certain gas types.

CADR doesn’t measure noise.

In order to test CADR rating, purifiers are run at their highest possible setting, which usually generates a lot of unwanted noise and isn’t practical for long-term use in your home or office.

In summary…

While CADR ratings can help you decide which air purifers are the most effective at removing pollutants, it isn’t the only factor to consider.  The right air purifier can make a huge difference in your family’s health and even emotional well-being. Make sure to do your research before deciding which one is best for your family.