Ambient filtering, not capture
Dust that a machine's collector or a tool's vacuum does not catch rises into the room. The fine part stays airborne long after the chips have settled, and that is what an air cleaner works on: a fan pulls room air through an outer filter and a finer inner one — on Grizzly's two models — and returns it. OSHA's preferred control for wood dust is exhaust at the points where it is produced, so an air cleaner comes after capture, not instead of it.
Grizzly is plain about the limits of its own G0572: it is designed only to capture dust from ambient air for a short time after cutting or sanding, and fine dust too small for its filter is blown back into the air. Grizzly says to wear a NIOSH-approved respirator while it runs and for a short time after. OSHA notes that respirators belong in a respiratory protection program in a workplace.
Two air filters by their maker's figures
| Model | Airflow by speed | Filtration as stated | Supply | Sound as stated |
|---|---|---|---|---|
| Grizzly G0738 | 260, 362, 409 CFM | 1 micron | 120 V, 1 A | Not given in the figures reviewed |
| Grizzly G0572 | 556, 702, 1044 CFM | 1 micron | 120 V, 4.2 A | 62–69 dB, no test conditions stated |
Figures from Grizzly's manuals for these two models only. The micron figure is Grizzly's own; it is not a HEPA or MERV rating.
How often it turns over the room's air
Grizzly's manuals give a simple method. Work out the room's volume in cubic feet and divide by the filter's CFM: that is the number of minutes it takes to pass the room's air through once. Divide 60 by that to get how many times an hour it does so. Grizzly's example is a 20 × 20 × 8 ft room — 3,200 cubic feet — and the G0738 on high at 409 CFM: about 7.8 minutes a pass, or about 7.7 times an hour.
Working out passes per hour, after Grizzly
Measure the room
Length × width × ceiling height, in feet, gives the volume in cubic feet. Leave out spaces closed off from the shop.
Divide by the airflow
Use the CFM for the speed you will run, as the maker states it. Room volume ÷ CFM = minutes for one pass.
Convert to an hourly rate
60 ÷ minutes per pass = passes per hour. A higher speed or a smaller room gives more passes.
Note— No target number
The arithmetic tells you how often the filter turns over the room, not how clean the air is. None of the sources reviewed sets a number of passes an hour for a woodshop, so BenchRoot does not suggest one.
Where to hang it
- Clear air in and out. Grizzly asks for at least 3 ft clear of obstructions in front of and behind the G0738; blocked airflow makes the unit short-cycle its own air.
- Near the dust. Grizzly suggests placing it in front of the machines that make the most dust, and positioning it so the room's air circulates past it.
- On structure. Hang it from load-bearing joists or studs — Grizzly asks for joists able to hold at least 100 lb each for the G0738 — never from sheet rock, pressboard or paneling alone.
- Clear of heads and work. Leave room underneath for people and long stock; check the clearance before fixing the chains.
Safety— What an air filter must not collect
Grizzly's G0572 manual forbids using it to collect silica, polyurethane, metal, lead paint, asbestos or hazardous bacteria; letting the filter take in explosive dusts, flammable or combustible liquids or fumes, burning or smoking material or toxic fumes; and connecting a machine directly to it. Keep it away from pilot lights and open flames. OSHA warns that accumulations of fine wood dust are a fire and explosion hazard, so clean the filters as the manual says.
Filter ratings
A micron figure is the maker's statement about its own filter. HEPA has a definition: the EPA describes a HEPA filter, as defined by the U.S. Department of Energy, as able to remove at least 99.97% of particles of 0.3 microns. MERV is a separate scale, rating capture of particles from 0.3 to 10 microns under an ASHRAE test method, and HEPA filters are not rated on it. One rating cannot be converted into another, so compare a filter only with one rated the same way.
Before hanging a workshop dust air filter
- Source capture on the machines and hand tools first
- Room volume and the filter's CFM, for passes per hour
- Joists or studs that carry the load; chains at a safe height
- At least the maker's clearance in front and behind
- No pilot lights or open flames nearby
- A respirator while it runs after dusty work
Capture at the machine is explained in the dust collector guide and, for hand tools, in shop vacuums. Sanding dust starts at the sander: see how to sand wood.
Sources
Airflow, filter and mounting figures are Grizzly's for its two air filters. The recirculation arithmetic is Grizzly's method; no source reviewed sets a target number of air changes for a woodshop, and BenchRoot does not set one. Filter ratings are given in each source's terms and not converted. No air filter was tested.
- 1.
Model G0572 Hanging Air Filter with Remote owner's manual (for models manufactured since 01/21). Grizzly Industrial, 2021.
Used for: A hanging air filter at 556, 702 and 1044 CFM with 1 micron filtration, 120 V, 4.2 A and a 62–69 dB rating; designed only to capture dust from ambient air for a short time after cutting or sanding; dust too small for the filter blown back into the room, and a NIOSH-approved respirator during and shortly after operation; mounting to load-bearing joists or studs, not sheet rock, pressboard or paneling; no silica, polyurethane, metal, lead paint, asbestos or hazardous bacteria, no explosive dusts, flammable liquids, fumes or burning material, and no direct connection to it.
- 2.
Model G0738 Hanging 3-Speed Air Filter owner's manual (for models manufactured since 4/15). Grizzly Industrial, 2015.
Used for: A hanging air filter at 260, 362 and 409 CFM with 1 micron filtration and a 1 A motor; room volume divided by CFM for the minutes per recirculation and 60 divided by that for times per hour, with a 20 × 20 × 8 ft example at 409 CFM; at least 3 ft clear in front and behind; placement in front of high dust producers; joists able to support at least 100 lb each.
- 3.
Wood Dust: Possible Solutions. U.S. Department of Labor, Occupational Safety and Health Administration.
Used for: Engineering controls with collectors at the points where dust is produced as the preferred approach; respirators within a respiratory protection program.
- 4.
Wood Dust: Hazard Recognition. U.S. Department of Labor, Occupational Safety and Health Administration.
Used for: Wood dust as a health hazard when airborne, and fine dust accumulations as a fire and explosion hazard.
- 5.
What is a HEPA filter?. U.S. Environmental Protection Agency.
Used for: HEPA as defined by the U.S. Department of Energy: at least 99.97% of particles of 0.3 microns.
- 6.
What is a MERV rating?. U.S. Environmental Protection Agency.
Used for: MERV as a rating of capture of 0.3–10 micron particles under an ASHRAE test, with HEPA outside the scale.
About this guide
Written by BenchRoot Editorial. How BenchRoot sources, checks and corrects its pages is set out in the Editorial Policy. If something here is wrong or unclear, the contact page explains how to tell us.