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Shop Air Filtration Calculator
A 22 x 22 x 9 ft garage holds 4,356 cubic feet. To turn the air over 6 times an hour you need 436 CFM, slightly more than one Grizzly G0738 on its top speed (409 CFM, 5.6 air changes per hour), so plan on two units or one unit plus careful dust capture. Air changes per hour equal CFM x 60 divided by room volume.
Air filtration ACHUpdates as you type
436 CFM needed: 2 filters at 409 CFM
- Room volume
- 4,356 cu ft
- CFM for 6 ACH
- 436 CFM
- One filter at 409 CFM
- 5.6 ACH
- Grizzly G0738 speeds in this room
- 260 CFM gives 3.6 ACH; 362 CFM gives 5.0 ACH; 409 CFM gives 5.6 ACH
- Air passes the filter every
- 10 minutes at the target
Air filters clean fine dust that a collector misses; they do not replace capture at the machine. The 6 to 10 air change range is a common shop convention, not a code value. Hang the unit where it can circulate the room, away from the collector exhaust.
Hanging air filters
Matched to this result.
Prices change often; the button shows today's price on Amazon.
Both ways to buy: Amazon and direct from Grizzly
Each card shows an Amazon pick and a Grizzly Industrial pick for the same job, with one line on when to choose which.
Hanging air filter
Both are 3-speed ceiling-hung filters in the 300 to 400 CFM class with remotes. The Grizzly unit is owner-rated 4.8 on grizzly.com across 301 reviews.
Prices change often and Grizzly runs sales, so the buttons show current prices.
What air changes mean
One air change per hour moves a room's whole volume through the filter once in an hour. Six is a common convention for a shop with light dust, ten for heavy sanding. The CFM you need is volume x ACH / 60. A filter ignores the dust that is still in the machine's hood, so capture at the source comes first and filtration second. A hanging unit like the Grizzly G0738 lists three speeds (260, 362 and 409 CFM), a 1 hour, 2 hour and 4 hour timer and a remote, which is why it is a popular pairing with a collector.
Placement
Hang the unit near the dustiest work, with room for air to reach its intake and away from the collector's exhaust. Run it on the timer for an hour or two after you stop cutting. A respirator is still the last line of defense for fine dust. See per-garage filtration sizing.
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Frequently asked questions
How many CFM for a garage air filter?
Volume in cubic feet times air changes per hour divided by 60. A 22 x 22 x 9 ft garage at 6 changes needs 436 CFM.
Does an air filter replace a dust collector?
No. A collector captures chips and dust at the machine. A filter cleans the fine dust that escapes into the room afterward.
What does the Grizzly G0738 filter?
The listing gives a 5 micron outer filter and a 1 micron inner filter, with three speeds from 260 to 409 CFM.
This page is researched guidance, not professional electrical, engineering or safety advice. Circuits, loads and clearances depend on your house, your service and your town: have a licensed electrician confirm any wiring, and check local code and each manufacturer's manual before you act.
