What does CADR stand for in air purifiers?

CADR stands for Clean Air Delivery Rate. It is the measurement of volume of air that is filtered by the air purifier. It is usually measured in three types, one for pollen, the next for smoke, and the last for dust. the number varies for each air pollutant. The higher number for the CADR denotes faster activity of the air purifier in cleaning the air. The measurement is taken in cubic feet per minute. CADR is a certification provided by the Association of Home Appliance Manufacturers (AHAM) that run a test on the air purifiers on its quality and efficiency. Look for the higher CADR or the air purifiers and that is easier when you compare one air purifier with another. 

Why CADR is important?

CADR makes it easier for you to choose the air purifier. Since higher CADR number means faster the air will be purified, you can choose the device accordingly. It also ensures that the device has undergone the test and has got a clean chit to be working efficiently.  There is no point in paying for an air purifier that cannot do much. The point is that, most air purifiers are almost the same in working mechanism, filters and make, it is the speed at which they finish the job is what CADR is all about and that brings the significant difference between them. 

How is CADR calculated?

The air purifier is run in a room whose area is pre-determined and the amount of pollutants is measured. The air purifier is run for a specific time period and after which the air contaminants are again measured. The reduction in the pollutants is used to determine the CADR. The CADR is also an assurance of providing that much amount of fresh air per minute of its working. 

Limitations of CADR

CADR certification is not fool proof. CADR is just another factor to help you choose the air purifier but is not the ultimate solution for the same. It is the result of the test done on the device and cannot say how long can the device sustain such performance. The air purifier may have an initial higher CADR but might decline over the period of time. This is where other factors also come into play. What makes an ideal or perfect air purifier for you is a combination of all the essential factors like purpose of the air purifier, coverage, energy efficiency, price, and CADR. 

Where to find CADR on the label?

CADR will be provided on the AHAM label of the air purifier. The AHAM label shows the 3 numbers of CADR for the three pollutants. To calculate the right CADR for your room, find the volume of the room, spot the CADR value and multiply this value with 12. The resultant number should be equivalent or higher than the room volume for the best results. 

What does ACH stand for in air purifiers?

ACH is the Air Changes per Hour. It is the number of times the air purifiers clean the full volume of a room in an hour. The air purifiers suck the air inside the room and clean it to give out clean air. The number of times this process repeated is significant in determining the ability of the air purifier. It is termed as ACH. More the ACH rate is better is the air purifier in cleaning the air and higher will be the quality of the indoor air. There are other factors that determine the ACH, namely, volume of the room and the output rate of the air purifier. 

Room volume, CFM and ACH

The efficiency of air purifier is based on the CFM of the device. The ability of the device in changing the air per cubic foot per minute is the CFM. This CFM is directly related to the internal fan installed inside the air purifier. More CFM value helps cover more area of the room. 

The coverage area and ACH are tightly related to each other. Here, lower ACH helps cover a larger area and higher ACH will cover a smaller area. The formula to find the room volume and ACH is, 

CFM x 60 minutes X ACH value

8 feet

ACH for asthma and allergy sufferers

An air purifier can cover a larger area of the ACH requirement is low. But there are target specific air purifiers like the one intended for allergy and asthma, such air purifiers will have a specific ACH rate. The expected ACH in an air purifier for asthma and allergy is 4-6 air changes per hour for more frequent air cleaning. These rates keep the air changes in every 10-15 minutes. 

The marketing tricks

The air purifier manufacturers often advertise the coverage area based on only 2 ACH. Read the label carefully and make your own calculations to check if the maximum coverage is exactly what you expect with the intended ACH. 

There also are some who mention the coverage area based on ACH, but must be keen to identify the difference. This helps save the customers money and prevent them from buying a larger air purifier when what they need was a smaller one. To prevent yourselves from getting fooled, always calculate the coverage in terms of room volume than the square foot area. The volume comes as a three dimensional calculation the mere floor area. Find the square foot area based on volume and ACH and not vice versa. 

Comparison helps

Never hesitate to compare the air purifiers. Go deeper into the actual values on the labels to see the real difference. Know your requirements before you go shopping. Distinguish them with these ACH, CFM, and room volume for accuracy.