shop-made air cleaner

Given your resources the key for your safety is a NIOSH-95 rated dust mask that fits well and is worn whenever you're in the shop. What is the particulate efficiency of the vac filter? You'll want a HEPA rated filter for maximum safety.

If you use the filter-and-fan, use a good quality filter like the 3M Filtrete 'Ultra Allergen' filter. This captures about 60% of the 0.2 to 2.0 micron particle size on the first pass, so it actually helps to improve the air -- marginally. And if you put that fan in the window to exhaust outdoors, make sure you make up the air from another open window so you don't end up with your combustion appliances 'backdrafting' into your house.

It is possible to make a shop-built air cleaner with 1/2 sheet of plywood, a couple furnace filters, and a discarded HVAC blower fan and motor. The fan/motor can usually be had for a case of beer from the local HVAC company. Again, the key to this unit's effectiveness is all in the filters you supply it with.

You will find an excellent online resource on dust collection at this site

I built one last Saturday from a single speed furnace blower, some left over lumber, some leftover paneling, silicon caulking, and (3) 20 x 20 x 1 pleated 3M allergen filters.

Works well except my blower is too strong, Blows tools off my peg board. It does clear my shop air in about 1 min though (12' x 16')

Most power tools don't generate that much fine dust that stays in the air for hours. Sanders are one of the exceptions. So why not make a downdraft/air cleanr unit that can also be an outfeed table for the table saw when needed. Furnace "blowers" can be had for a song and used pleated truck air filter cartridges or spa/pool cartridges will catch the really fine stuff before they get to your lungs.

Here's one that you can make that works - if you use it.

My vac filter is HEPA (99+% to 0.3 microns) and the filters I bought to put on the fan are the 3M Filtrete allergen type. I was thinking of maybe putting the fan with filter somewhere in the middle of the room (pointing away from me to avoid blowing other dust into my face) and a different fan pointing out the window? There is a door up the stairs that would allow some cross-ventilation and should prevent negative pressure/backdrafting. If I use the filter/box fan idea, would there be an advantage to building the fan into a plywood box with the filter on the intake end, as opposed to simply taping the filter to the fan? Is the HVAC blower fan better just because it's a stronger fan?

My vac filter is HEPA (99+% to 0.3 microns) and the filters I bought to put on the fan are the 3M Filtrete allergen type. I was thinking of maybe putting the fan with filter somewhere in the middle of the room (pointing away from me to avoid blowing other dust into my face) and a different fan pointing out the window? There is a door up the stairs that would allow some cross-ventilation and should prevent negative pressure/backdrafting. If I use the filter/box fan idea, would there be an advantage to building the fan into a plywood box with the filter on the intake end, as opposed to simply taping the filter to the fan? Is the HVAC blower fan better just because it's a stronger fan?

No real advantage. Just tape a cheap filter ahead of the high-effeciency filter, so you don't have to change it so often.

Is the HVAC blower

Yes, it moves a greater volume of air. But do experiment with your box fan, you may find it is satisfactory.

steve

The box fan with a furnace filter works well. I recommend a regular furnace filter (the cheap kind) and replace them often. A clogged filter does no good and will tax the fan motor. A couple light-weight bungee cords will secure the filter in place.