Here’s the HTML article on sizing a basement air filtration system, covering CADR targets, the EPA sizing table, and common mistakes to avoid.
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Size a basement air cleaner by matching its smoke CADR in cfm to your floor area — about two-thirds of the square footage.
Most basement air cleaners disappoint for one boring reason: they’re too small for the room. An undersized unit never catches up, so it runs constantly, clogs its filter early, and still leaves the air stale.
The math behind how to size an air filtration system for a basement is short and public. Measure the space, pull the minimum smoke CADR from EPA’s table, and buy a unit that meets or beats it. Five minutes, no guesswork, no sales pitch.
How Much Air Cleaner Does A Basement Need?
CADR stands for Clean Air Delivery Rate and is measured in cubic feet per minute. The number describes how much contaminant-free air a unit delivers for a defined particle-size range, which is why it beats any claim printed on the box. AHAM, the group that runs the testing behind those ratings, publishes what the figure does and doesn’t tell you. EPA states the relationship plainly: room area in square feet equals 1.55 times smoke CADR, the same as saying a unit’s smoke CADR should land near two-thirds of the floor area.
| Basement Floor Area | Minimum Smoke CADR |
|---|---|
| 100 sq ft | 65 cfm |
| 200 sq ft | 130 cfm |
| 300 sq ft | 195 cfm |
| 400 sq ft | 260 cfm |
| 500 sq ft | 325 cfm |
| 600 sq ft | 390 cfm |
Sizing A Basement Air Filtration System: Where The Numbers Come From
Every figure in that table assumes an 8-foot ceiling and a fully measured space. Measure the whole area the cleaner will serve, not the corner where you plan to plug it in.
- Measure the basement’s length and width, then multiply for square feet.
- Open floor plan? Include the entire connected space the unit will clean.
- Ceiling above 8 feet? Switch to volume and target air changes per hour instead of floor area.
- Compare your total against the maximum recommended room size on the packaging.
- Buy a unit whose smoke CADR meets or beats the target for that size.
EPA’s Guide to Air Cleaners in the Home is the document behind all of this, and it’s worth reading once before you buy. The same guide flags the case most people miss: a taller basement ceiling means floor area alone will undersize the unit, because the cleaner has more cubic feet of air to turn over.
Once your number is set, the tested basement air
