Purchasing an appliance like an air purifier comes with technical jargon that can get confusing. So it’s easy to glaze over and tune out when a salesperson or company representative starts talking about CADR, ACH, and CFM.
An air purifier CFM stands for “Cubic Feet per Minute” and is a way of rating an air purifier’s ability to circulate air. The higher the CFM, the more air is circulated every minute. CFM is a significant number to note when deciding which air purifier works best for your space.
This article will help you understand what CFM means and how it affects your air purifier purchase.
What is Air Purifier CFM?
The CFM rating on an air purifier indicates the volume of air the device can move in a minute. The higher the CFM number, the more influential the device.
When shopping for an air purifier, you’ll want to take the time to find one that’s appropriately sized for your needs. If you choose a unit that’s too small, it won’t be able to effectively purify the air in your space.
On the other hand, if you select a cleaner that’s too large, it will cycle through the air in your area too quickly and won’t have enough time to filter it properly.
You’ll need to know the square footage of the space you want to purify to find the right CFM for your needs. Once you have that number, you can consult a chart that tells you how many CFMs you’ll need to effectively clean the air in your space.
The ACH number tells you how often the unit can cycle through the entire air volume in your space in one hour.
For example, if you have a 500-square-foot room and want to cycle the air in that room five times per hour, you’ll need a unit with a CFM of 100.
To find the ACH number, multiply the square footage of your space by the number of times per hour you want to cycle the air.
Formula To Calculate Desired CFM
To identify the CFM rate of an air purifier, you can use this formula:
CFM = Length x Width x Height x (Air Changes per Hour) / 60 min.
Before going to the store and shopping for an air purifier, you must identify your space’s square footage. To do that, you need to know the length and width of the area in feet. Once you have those numbers, multiply them together to get the square footage.
For example, if your room is 12 feet long and 12 feet wide, the square footage would be 144.
Now that you know the square footage of your space, you need to decide how often you want the air to be cycled. The standard is two to three times per hour.
For our example, we’ll use three.
Now that you have your room’s square footage and the number of times per hour you want to cycle the air, you can plug those numbers into the formula to find the CFM.
For our example, the formula would look like this:
CFM = 144 x 3 / 60 min.
This equals 7.2 CFM.
This means that you need an air purifier with a CFM of at least 7.2 to effectively clean the air in your space three times per hour.
What is a Good CFM for an Air Purifier?
The CFM would greatly depend on the size of your space and how often you want to cycle the air.
As mentioned, the general rule is to have two to three air changes per hour. However, some spaces require more or less depending on the level of contaminants in the air.
For example, if you live in an area heavily surrounded by outdoor pollutants, you may want to cycle the air more often than someone who lives in a rural area with clean air.
The type of space you’re purifying also affects how often you should cycle the air. If you’re trying to filter a small space, like a bathroom, you won’t need to cycle the air as often as you would in a larger area, like a living room.
A good CFM for an air purifier is anywhere from 4 to 8.
Air purifiers like the Blueair Classic 490i have some of the highest CFM. This unit has a CFM of 500 and can cycle through the air in a space of up to 600 square feet three times per hour.
For larger spaces, it’s essential to identify the units with the highest CFM. For example, the AirDoctor 5500 has a CFM of 1000 and can cycle through the air in a space of up to 1500 square feet three times per hour.
Is CFM the same as CADR?
CADR is the Clean Air Delivery Rate, a rating system that tells you how well an air purifier can remove specific contaminants from the air.
The CADR is determined by testing the unit in a sealed room with specific levels of pollutants. The results of these tests are then used to determine the CADR rating.
The higher the CADR rating, the more influential the unit is in removing specific contaminants from the air.
The CADR rating is essential, but it’s not the only factor you should consider when choosing an air purifier. The CFM is also essential, especially if you’re trying to purify an ample space.
For example, an air purifier with a CADR rating of 250 for smoke may not be as effective in a spacious room as an air purifier with a lower CADR rating but a higher CFM.
Asking your HVAC technician would help you identify the air purifier you need.
