wye, oh wye, oh wye is there dust unto dust

[Alan Schaffter]

Due to low CFM, once further than 1/2" or so from the holes the dust won't be captured. The dust may not spray out at you, but you will still be left with a pile of it on top of the board and around the guard. And remember, and VERY IMPORTANTLY, most of the time boards being cut will cover most of the holes!

[Bruce Seidner]

Let us know so we can still help, and question your sanity.

I have been assembling what I will need to do the heavy lifting in the shop and have a cyclone, 5hp 14" blower, and a local source for 6" S&D PVC.

I noticed the apparent popularity of shop air filters but it is counter intuitive to hang them from the ceiling where they look like they would "stir the pot" in a shop as much as they would filter the air.

Remembering the Jen-Air down draft cook top that did such a great job with the smoke off an indoor grill it seemed to make sense to have an overall "ambient" shop filter closer to the source at the "cook top" bench of a wood shop.

So, to be more clear, I am not thinking about primary dust collection, but of secondary collection and filtering. I have low ceilings in addition to my native ambivalence about these ceiling hung shop filters.

Clearly I have learned that small ports or a long slit of a port would be useless for even auxiliary dust collection at a source like a tool or even hand sanding. This is the job of a primary collection port.

But I am still thinking it makes sense to have the secondary ambient filter inspiration close to the bench and distributed, filtered, and expired in a way that was difused and would not be a hanging box from the ceiling.

[Alan Schaffter]

I have one but rarely use it.

There are some facts about air cleaners most people don't know, didn't realize, or just ignore, so read on. First, if they didn't aleady know, everyone here now knows the goal is to collect as much dust as you can, especially the fine and dangerous .5 - 10 micron dust, at the source , hence good CFM and good hoods, shrouds, ports, etc. at each machine.

All but the best air cleaners, may in fact be WORSE than having no air cleaner at all. What!!! What you talkin' bout Willis? You got some splaining to do, Lucy!

Stay with me here. Since most dust is generated at or near waist height. And unless your shop air is circulated by some mechanical means (fans, etc.), the dust will generally stay at waist level and below as it settles. So what does an air cleaner do? It circulates air. Hmmm, ok, but isn't that ok since it filters out the baddies? Only if ALL dust laden air is sucked through its filter, and then only if the filter is good down to .5 microns!!!

The claims by air filter manufacturers that they filter the air in a certain sized shop X times every hour are misleading. First, it is probably an inflated figure like many in this business, but if it is valid, it is only so when the filters are new/clean. But the biggie here is, that figure doesn't mean every liter of air passes through the filter X times in an hour. It only means that "a volume of air equivalent to the air volume of your shop" passes through the cleaner X times every hour. It could be that some liters of shop air pass through 30X times while some, not at all!!! Just look how close the intake is to the exhaust of a typical air cleaner- less than two feet away. So, as a reasonable person, do you think dust laden air billowing around your disk sander way over yonder will be sucked up as often as the air that just left the cleaner, IF AT ALL?

As to filters- typical furnace filters are barely good enough to stop small birds. Seriously, unless you get the EXPENSIVE HEPA filters and use a multi-stage filter stack, you are just circulating and stirring up dusty air. AND since the fine dust can stay airborne by itself for 30 min. or longer, you are now helping it to stay airborne much, much longer, you are giving yourself many more opportunities to breathe it! The ugly truth, air cleaner manufacturers don't tell you.

Frankly I use mine help keep the shop clean when I'm not there and don't even consider that it will protect my health. I have my air cleaner on a timer. I turn it on when I leave my shop and it turns itself off 1 - 2 hours later.


That's my story and I'm sticking to it!

[Bruce Seidner]

Alan has just fully explained the spirit of my concerns and the basis of my thinking about a long slit tube that wraps the wall edge of my corner bench rather than a ceiling box that I would constantly bang my head on and which would do marginal good for my lungs.

I was thinking that this slit pipe would be powered by it's own fan or blower into a 1micron filter bag. I really liked the folks at American Fabric Filter Co. who were very kind and flexible and sold me 90sq feet of fabric for the filter bag I am constructing for my cyclone/blower. I plan to tap them again for this room filter. My thinking is that I will get a wide but shallow input of air that will be pushed through another long filter tube in my crawl space. This air will find its way back to the main shop area at its own leisurely pace. I am trying to play a bad hand well by exploiting this adjoining crawl space to do things that would be unreasonable with a conventional floor plan.

I just picked up this SKY EAGLE TOOL KING USA 3/4 HP / RPM 3405 / 3105 / 2600 / AMP 7 / 6 / 5.5 / 3 SPEEDS blower for $30 and it is wild. It is made to power those huge fabric inflatable sky dancer thingie's and I reckon if it can keep Santa afloat it can be put to better use filling a filter bag with shop air. It seemed like a good idea at the time. I'll see if it actually works. But it was cheaper than the squirrel cage fans I was finding and it is a veritable hurricane when you turn it on. I think this is what we would call off label use in medicine. But I want to avoid the problems that I saw but could little explain in conventional room air filters.