Air Filtration units (overhead ones)

[Daryl Negley]

Does anyone on here have any experience with air filtration units that are mounted to the ceiling? Is there a minimum distance from the floor that they should be mounted in order to achieve maximum air filtration? Is there a way to determine if certain units will move enough air for the size of my shop?

As you can tell I have a few questions.......any help would be appreciated!!!

[Adam Strong]

Most units recommend between 8 and 10 ft above the floor, but also say they can be used on the floor. I think in most cases head room will be the primary concern. Location can affect the air circulation of the shop, meaning you may have some dead air spots... optimal location can vary. As far as moving enough air for your shop, the CFM rating will give you an approximation of that. Just figure the volume of air in your shop, comparing with the cfm of the unit will tell you how long it takes to cycle all the air in your shop.


example: a shop that is 20'x20' with a 10' ceiling is 4000 cubic feet. A unit with a max 750 cfm can theoretically cycle all the air in the shop in 5.33 minutes.

[JohnT Fitzgerald]

I can't say with any certainty what makes one location work better than another, but I have seen a lot posts by people that put them pretty much anywhere - flush along a wall, on a ceiling, or even mounted under the extension wing of a table saw.

Mine (a Jet AFS100B) is mounted to the ceiling joists in my basement shop. It's 7.5' to the joists, so I have about 6.5' to the bottom of the unit. I've hit it a few times so far with 'stuff', but in general it seems to work OK.

[Kent A Bathurst]

My JDS 2000 is suspended from 8'6" joists. I have it dierctly over the TS, so I can't whack my head on it.

[Peter Aeschliman]

These units are good to have as a backup to primary dust collection. So just a warning that they aren't a substitute for a true dust collector with ducting/etc.

There are also other things to think about. For example, just because the math that Adam did above tells you that it can exchange all of the air in your shop in 5.33 minutes, that doesn't mean it will actually do it.

The reason is a flaw they have in their design from the get go: The intake and exhaust are close together. It will recycle the same air over and over, while other areas of the shop may not get recycled. I've read this analogy: It's like taking a glass of water, holding it under the faucet and letting it overflow. Some of the water in the glass may be replaced by incoming water, but not all of it.

The way around this is to plumb in some ducting on either the exhaust side or the intake side so that the intake and exhaust are on opposite sides of the shop from each other, and so that it causes the air to swirl around your shop in a circular motion (i.e. around the perimeter).

I have a Jet air filter unit, and here I am on the soap box... but haven't gotten around do doing this myself! ha ha

[Kent A Bathurst]

.......The intake and exhaust are close together. It will recycle the same air over and over, while other areas of the shop may not get recycled...

Everything in your post is exactly correct IMO, Peter. Not a single argument.

I do have one thing to add - I have a cyclone for the big iron. My JDS intake is less than 6' as the crow - or dust - flies from my primary workbench where I do all my hand + ROS sanding, and routing. Those operations seem to me to be the big generators of airborne fines, and that intake sucks 'em up - not all, not all, I know - but still.....

[Eric Gustafson]

The finest particles in shop dust stay suspended for extraordinary lengths of time. We are talking on the order of a couple of hours to 3 days for the finest particles. The larger particles fall out of the air by their own weight. An air cleaner get the finest particles. Hanging it near the ceiling is best. If you put it under your table saw it will choke up quickly with even the coarse dust. DAMHIKT!

Also, if you install it so it tends to cause the air to rotate in the room, it will be more effective.

[Steve Kohn]

The finest particles in shop dust stay suspended for extraordinary lengths of time. We are talking on the order of a couple of hours to 3 days for the finest particles. The larger particles fall out of the air by their own weight. An air cleaner get the finest particles. Hanging it near the ceiling is best. If you put it under your table saw it will choke up quickly with even the coarse dust. DAMHIKT!

Also, if you install it so it tends to cause the air to rotate in the room, it will be more effective.


Another thing to consider if your shop is heated. The warmer air will be up by the ceiling. A fan mounted on the ceiling circulates the hotter air and makes the shop temperature more consistent. I have my air cleaner (Jet) on whenever I am in the shop more from the heat circulation than to clean the air.

[Bill Blackburn]

.but if that air is hot and humid in the summer I run mine way less for the same reason

[Van Huskey]

The way around this is to plumb in some ducting on either the exhaust side or the intake side so that the intake and exhaust are on opposite sides of the shop from each other, and so that it causes the air to swirl around your shop in a circular motion (i.e. around the perimeter).

I have a Jet air filter unit, and here I am on the soap box... but haven't gotten around do doing this myself! ha ha


Until you get around to the "fix" just having a fan moving air in the shop will help.