Home made air cleaner

[dlminehart]

I'm looking at building a shop air cleaner. To save money and space, I'm trying to figure out a way to get more than one use out of the cabinet, while not hurting the primary function of cleaning the air.

Does it make much difference whether the air cleaner is by the ceiling or floor? Since air must flow through the cabinet, I assume one needs clearance both in front and behind. How much would be adequate?

I'd assumed I'd use two filters; first, an inexpensive one to catch the bigger stuff, and then a higher quality (HEPA?) one to catch the fine stuff. Any reason to not just use the standard furnace-type filters found at the BORG? I noticed in Tom Clark's "Practical Shop Cabinets" book that he used these special 4" wide pleated air filters, mail order from Iowa. Any advantages?

Any suggestions for making additional use of the cabinet if I go with a floor-mounted one? Seems that the air chamber's size is pretty irrelevant, so there'd likely be room for drawers above the filter area.

[gsmittle]

I'm looking at building a shop air cleaner. To save money and space, I'm trying to figure out a way to get more than one use out of the cabinet, while not hurting the primary function of cleaning the air.

Does it make much difference whether the air cleaner is by the ceiling or floor? Since air must flow through the cabinet, I assume one needs clearance both in front and behind. How much would be adequate?

I saw a picture of a shop-built air cleaner (Maybe Tom's book?) that exhaused the air vertically, so you could put the cleaner up against the wall and then you would only have to make sure there's clearance in the front.

g.

[LCHIEN]

I've seen some plans where they built the fan and filters into a work table.
Doesn't need to be high.

[Pappy]

Another variation on the work table filter is to make the intake from the top to double as a downdraft sanding table.

[radhak]

This page on the site of Kevin S. Brady, Esq has some good info : he started with a regular unit then enhanced it to exhaust upwards.

He even offers dimensional drawings in pdf format.

(further explored the site : he's spent extensive time and effort in building it on a variety of subjects - even got some recipes for chipotle's chili )

[radhak]

And I have always wondered if using any old fan would work.

This tip from shopnotes seems to say it would...he's used a regular box fan! Have to try it.

[radhak]

Another example at lumberjocks. (Sorry, a bit too much of googling ).

He's used two pre-filters and and one post.

[linear]

Here's my version: http://www.bt3central.com/showthread.php?t=24144

I used two pleated filters in series like you asked about. The outer is a cheaper kind rated for larger dust and the inner one is one of those high-dollar ones. The outer one gets clogged and the inner one is still just slightly discolored, so I suspect this is working out well.

Some fans will do better than others under load. Don't just compare the CFM rating numbers. Also fans are rated for CFM in free air, which is not what you'll get with a filter and a box attached, so adjust your expectations accordingly.

[Uncle Cracker]

I had a friend (dead now) who made one out of an old A/C air handler. He ripped out the refrigerant coils and the plumbing, and shortened the cabinet. Then he stacked three filters... A standard fiber filter was the first stage, then a corrugated paper filter as the second stage, and finally a HEPA filter. His theory was that the majority of changes would be of the cheaper fiber filter (actually, it turned out that the paper filter in the middle that clogged up the quickest). He built an intake platform under the unit at floor level, then directed the output air (coming out of the top) to the opposite side of the room with some homemade MDF vanes. This was so the air in the room was more fully cycled. It did take up too much room, so eventually the whole thing ended up under his workbench, with a fabricated sheet metal output duct running up to the ceiling between two wall studs. To each his own, but I think I would have just hung the whole thing horizontally from the ceiling...

[linear]

I contemplated making 5 of the six sides of mine filters.

There were two reasons I didn't go that route:
I wanted to keep the same size as what I already buy for my furnace (I find it easy to buy furnace filters 6 at a time or so--usually I just take all that are on the shelf when I think to buy them). And the scrap material I had on hand lent itself better to the shape I made.

I think all filters except the fan mount side would be an advantage. Four sides made from 20x25 and one end made from 20x20 pleated filters should do nicely. You could even just duct tape the whole shooting match together.

I also considered that the commercial units would probably be designed that way if there were an appreciable performance advantage (after all, they'd sell more consumables).

I thought I had posted this pic in the other thread, but I didn't. It works real well:

[dkerfoot]

And I have always wondered if using any old fan would work.

This tip from shopnotes seems to say it would...he's used a regular box fan! Have to try it.

I am planning on doing something similar - bungee a furnace filter to the front and back of a box fan. Probably go with a cheap one on the intake and one that blocks smaller particles on the output. Not planning on rafter mounting it, just set it where most needed. Not very impressive looking, but sometimes cheap and simple is a good thing.