Clean air is vital for your health and well-being, especially indoors, where most of us spend the majority of our time. One effective way to improve indoor air quality is by using an air filtration system that matches the size and ventilation needs of your space. This guide will help you understand how to calculate the correct filter size based on CFM (Cubic Feet per Minute) and your room volume, and why it matters.
Understanding Room Volume and CFM
Room volume is the cubic footage of a space:
CFM (Cubic Feet per Minute) is how much air an air filter can move in a minute. The higher the CFM, the faster the air in the room is filtered.
Basic Air Filter Calculation
To find the air changes per hour:
If your room is 30′ x 40′ x 8′:
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Room Volume = 9,600 Cu Ft
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Filter CFM = 2,000
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9,600 ÷ 2,000 = 4.8 minutes per recirculation
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60 ÷ 4.8 = 12.5 air changes per hour
That result is more than sufficient, as the recommended minimum is 6 to 8 air changes per hour.
Why Maximum Room Cubic Feet Matters
Every air filter has a recommended maximum room size it can effectively handle. Exceeding this limit will reduce performance and air quality. A quick way to estimate this is:
Examples
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G0738 Air Filter – 409 CFM → Max Room Size ≈ 4,090 Cu Ft
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G9956 Air Filter – 1,400 CFM → Max Room Size ≈ 14,000 Cu Ft
Using Multiple Filters
If your space exceeds the capacity of a single unit, consider using multiple air filters to increase coverage and efficiency.
Quick Formula to Estimate Air Circulations
Aim for 6–8 air changes per hour for effective air purification.
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