The CADR Air Flow of Air Purifier
Now that you have a handle on the air purifier filters, we need to explain why you need to move the air through the filters.
Without sufficient air flow you will not see the dust removal you are looking for. This is challenging in any room since there is often air mixing in from other rooms. Or perhaps for forced-air heating system is circulating air throughout the house. Without enough clean air changes in your room, it will not be clean.
One way to measure an air purifier's ability to move the air through the air purifier filters is the metric called the CADR.
CADR stands for Clean Air Delivery Rate. This is measured in cfm or cubic feet per minute. It's like a cfm air flow number.
Where it gets confusing is in determining how this number relates to the sq ft size of your room.
Obviously, if your room is sized 15 ft by 20 ft it is 300 sq ft. But the CADR rating is in cubic feet per minute and not square feet per minute. So, to convert the room size to cubic feet multiple the sq ft number by the ceiling height. This will often be 8 or 10.
To keep the math simple, let's use 10. Your 300 square foot room with 10 foot ceilings has 3,000 cubic feet to clean.
If the air purifier can deliver 300 cfm (CADR) then it will take 10 minutes to clean the air in the room once. At this rate it will filter the air 6 times per hour.
Click on this link to learn more about air purifier room size and square footage coverage.
We see some brands promote one air change per hour up to five air changes per hour. To get the air cleaning you desire you will get better results with a higher CADR rating.