My homemade indoor venting filter

[Dan Hintz]

Since the average daytime temps here in MD are in the high-20's range, venting to the outside (and therefore sucking in cold air to replace what I'm venting) not only lowers my average indoor temps to unacceptable levels, it raises my bills. What's one to do? Well, this engineer decided to pull a MacGyver and put together a makeshift filter. At the moment I only do items that give off particulates rather than fumes, so venting indoors isn't an issue.

Here's the parts list:
2 * Register Boots @ $6/each
2 * 6"-to-4" Reducers @ $6/each
1 * A/C Filter Cloth @ $6
1 * Hardware Cloth, 1/4" Hole @ $10

The register boots are what's behind the wall vents for your A/C system, basically turning a 6" tube into a 6"x10" rectangle. I cut the corners back about 1/2" and folded the new flaps 90 degrees outward to make a mating surface all around. I cut out a matching size of filter material and wrapped it on either side with the hardware cloth (wire mesh) like a taco. This was sandwiched between the two register boots, and the newly created flanges were held together using large binder clips (i can take it apart easily to swap out the filter material and to see what gets caught in it). The reducers go on either side to bring the piping back to 4" diameter.

To be fair, the reducers were not designed to fit right onto the boots (some 6" pipe is expected between them), but with some slight crushing of the metal they slipped on and were duct taped to prevent any major leakage. I've attached this directly to the Harbor Freight blower I picked up, with a few feet of spiral metal tubing to the laser. It seems to pull a good enough vacuum, but I'd still like to move to a self-contained unit that deals with fumes, as well, but cost on those is pretty high.

For $40 or so, I think it was a good deal

[Dan Hintz]

Well, this designs seems to be working fairly well for me, but it's time to upgrade it to something that can handle some of the nastier materials (wood, acrylic, etc.). I'll add to this as the build proceeds, but the final additions will be an activated carbon chamber, a HEPA filter, and an electrostatic precipitator.

[William Palm]

Good idea! Have you tried using a charcoal filter from like an oven hood in your kitchen and cheese cloth is good for finer particulates. The other option is renting or purchasing a smoke eater when doing items with more smoke.

[Dan Hintz]

You need a lot of charcoal to take care of the fumes, unless you want to be replacing those filters every day... think like 20-40 pounds worth.

[Mike Burroughs]

I have the charcoal filter unit (from sign warehouse)....and maybe im missing something, but my shop still smells after lasering certain items, even wood. The only thing I haven't checked yet is maybe the charcoal has settled or needs to be replaced.

mike

[Dan Hintz]

Mike,

Weigh the charcoal... when it doubles in weight, it's time to replace it. Are you sure you don't have any leaks in the vent system? Even the smallest of holes lets out a surprising amount of stink.

[George Brown]

I have the charcoal filter unit (from sign warehouse)....and maybe im missing something, but my shop still smells after lasering certain items, even wood. The only thing I haven't checked yet is maybe the charcoal has settled or needs to be replaced.

mike

You won't be able to get rid of ALL the smell. The wood as you take it out of the laser has some smell to it. I laser LOTS of wood, and while there is some smell, it it not obnoxious.

[Dave Johnson29]

and while there is some smell, it it not obnoxious.

Hi George,

The filter may not be as effective as hoped and that if you could smell wood fumes, you could be ingesting other harmful stuff without smelling it or knowing about it.

Some dyed (not sprayed) white leather for instance gives off Chromium Cyanide and you would not smell it.

[George Brown]

Dave, some wood smell is inevitable, as the wood itself, once lasered, has the smell. It not longer emits smoke, but the smell is there. I've never lasered leather, but would assume that chromium cyanide would only be emitted while lasering, once it stops smoking, it should not emit any more.

[Dave Johnson29]

but would assume that chromium cyanide would only be emitted while lasering, once it stops smoking, it should not emit any more.

That's true George, but the point I was trying top make is that if you can smell wood smoke before you open the lid of the laser then the filter piping is either leaking or the filter is not effective enough.

Either way that would have to be rectified before cutting something that gives off toxic residue of some sort, speciflcaly if you cannot smell the toxic stuff.