Ceiling-mounted dust collectors

Recommedations on where to buy and how to build. January 16, 2002

I have a 3000 square foot shop with 2 10-foot sliding table saws at one end using 1000 square feet. My ceiling is 12 feet high. I would like to use a ceiling mounted unit to clean secondary dust that the dust collectors miss. Any advice on what type of unit to get and what size?

Forum Responses
I built one from a piece of house heating duct, mounted 2 barrel fans (from a side-by-side fridge) on a piece of plywood with exhaust holes cut. Stacked 3 furnace filters on the other end. It collects dust big time--I need to change filters monthly. I am moving into a shop the same size as yours soon and will be installing 6 units. I found some small blowers at a surplus store, 600CFM, $10. They are from a large IBM computer.

Ceiling mounted air cleaners are an excellent addition to dust control. Delta has a nice economical unit, Model 50-860 Air Cleaner, 850 CFM. In our spiral manufacturing department we utilize an air cleaner manufactured by Airflow Systems in Dallas, Texas. They manufacture a range of different size units according to air volume required. The size of unit depends on the cubic area of shop space that needs to be cleaned approximately once every 5 minutes. Our Airflow unit has been running for over 2 years, 5 days a week, 10 hours a day. It is very low maintenance and does a wonderful job keeping the air clean. These types of units are not just hung randomly. They are many times positioned to create a circular airflow around the room, almost like a whirlpool effect.

Curt Corum, forum technical advisor

You can make your own but keep in mind that what needs to be removed from the air are the small particles, around 1 micron in size. The cheap glass furnace filters will not do that. Also, when you get into a 1 micron filter, the standard furnace blower will not move the air because of the static pressure across the filter. It is not as easy as it seems.

Most woodworking catalogs advertise dust filters that remove some percentage of the 1-5 micron particles. They usually filter 200 to 400 cfm with two or more filters and cost $250 up. Really good filters with 800 cfm and up cost much more.

I have a 20' X 24' garage and designed and built a 1,200 cfm dust filter for under $100. The main part of the advertised filters is a squirrel cage blower powered by a small electric motor. The same blowers operate forced air furnaces where the first thing to fail is the firebox. The minimum sized furnace blower is 1,200 cfm. When furnaces are replaced, the case and blower are scrapped. A local furnace dealer gave me the blower and wiring if I would remove it from the furnace carcass.

I designed a plywood case to hold the blower, which takes in air from both sides, so a clearance on each side of about 3" does the trick. Most blowers can be any side up (check the name plate) and run on 110V. There is a 1" space between the blower case and the extended bag filter. The bag filter is held in place by a channel made of 3/8" strips glued around the inside, on both sides of the bag filter sheet metal frame. A third row of strips holds the pre-filter just inside the inlet opening. The case is 40" long X 21" wide, 14" high at the filer end and 19" high at the blower end. Of course a filter has to be dimensioned to fit the blower and the filters.

The following purchases completed the project:
1. 5/8" 5 ply plywood, hinges and a latch for a double hung window.
2. A bag filter (removes 98% of particles 3 microns or larger) and a pre-filter from Penn State Industries for $35.00
3. A rotary one-hour manual switch from Home Depot. This allows you to run the filter after you have left the shop to really clean the air, plus a 3 wire cord and plug.
4. Screw eyes for the filter and screw hooks for the ceiling.
5. A 7 1/2" X 9" adjustable louver for the outlet end of the blower from Home Depot.

The box was glued together using biscuit joints to make it reasonably airtight. A door was hung on the side to allow the filters to be removed and cleaned or replaced. The exhaust end was screwed to the case to allow for blower removal if it ever wears out. The filter should be placed close to the ceiling and close to a wall-near the middle to do the best job of cleaning all the air in the shop. It works great, there is no fine layer of dust on my car, and no noticeable draft while working.