polyurethaneprotection
Cans of polyurethane state a number (250, 350, etc) of Volatile Organic Compound (VOC).
When sanding wood, a NIOSH N95 is required to safely avoid inhaling the small particles, but..
Does a NIOSH N95 stop VOCs? I am guessing that the airborne molecules are far smaller than the 0.3 micron size that such a mask is meant to prevent. Can you confirm that this guess is accurate? Are there other masks that will catch the VOCs, or is keeping the area well ventilated the best that one can do?
Spray foam insulation for large areas with a closed-cell foam tends to be a job performed by professionals. They will mask off the area being sprayed, and bring in a bunch of specialized equipment to do the job fast. The result doesn't require a separate vapor barrier since closed cell foam is a barrier. It does have the downside that any future repairs or renovations will require a significant effort to remove the foam.
The main reason to spray foam an attic space is to make the area a living space and eliminate the need to ventilate under the roof (typically done to prevent ice dams). To do this, they would spray directly under the roof, between the rafters, rather than between the joists. Otherwise, the traditional solutions are blown and fiberglass insulation.
Blown insulation requires the vapor barrier to be put down first, soffits to be protected so they aren't covered over, and then a machine can be rented to blow in as much insulation as you like. The advantage of blown insulation is speed, fewer gaps in the insulation, and it's easy to add a few extra inches. If you ever need to remove a ceiling under blown insulation, it becomes difficult since you first need to remove all the insulation unless you want it falling into the room below.
With fiberglass insulation, the vapor barrier is often attached, but it needs to be stapled to the joists, which is difficult to do from above. It's much easier to temporarily move out of the way for a repair or renovation, but it's also easy to leave small cracks where moisture and heat can escape.
If your problem was that you had wind blown rain entering from your soffits, then you may need to add a baffle or some other storm resistant vent that blocks the wind driven rain while still providing fresh air all other times.
I believe you are using the tool wrong. With a sawsall I have seen many people try and hold the saw in place, I am a big guy 6'5" and close to 300lbs and I could do this for a few minutes but prefer to use the guard to stop the tool from pulling my arms around. Push the guard up to the work and don't try to feed two fast or it will push back. When properly cutting it takes very little effort to hold the tool in place and let it do the cutting. If you do not use the guard to keep the tool from moving the sawsall is putting your arms through what it would take to cut using a hack saw. Keep the saw tight to the work and let it do the work.
Best Answer
Yes, their are things that help with polyurethane fumes, masks with volatile organic vapor cartridges, usually activated charcoal.
VOCs are not particles of "stuff" so a particulate filter (N95, P95, Etc) does not help with them. This means a typical size in microns is also irrelevant because you are dealing with molecular size when it comes to vapors.
The particulate filters help with solids like dust and dirt, but not vapors.
Organic vapor cartridges absorb the vapors in the cartridge like a sponge absorbs water. A sponge does not clog like a filter but gets saturated. An organic cartridge also gets saturated by vapors and eventually needs replaced; but not because it is clogged.
You use a pre-filter with organic vapor cartridges to capture the particulates (solids) before the vapor cartridge.
I use a 3M half face mask with a 3M organic vapor cartriges and P95 prefilters for things with VOC's. I can spray cabinets with laquer (lots of VOCs) inside and not smell a bit of the fumes where my wife walks in and almost gets knocked over by them. Since paint has VOCs we also use the same organic cartridges when spraying the interior of a house.
The mask can also take particulate filters so we use those as well when in really dusty environments for prolonged periods of time such as during demo during a remodel. Remodel dust does not have any dangerous vapors (they have already vaporized) so we do not need the bulkiness of the organic cartridges.