What to do when spray foam has been removed and still have bad smell

Where isocyanate comes from

Epoxy has 2 toxic halves that react with each other. When they do, the result is so non-toxic it's used to line food and soda cans. They are reacting to form a very long-chain molecule, which is very strong and tough.

The 2 parts "hold hands" like this: A-B-A-B-A-B-A-B-(repeat a lot)-A-B-A. They don't have to be infinitely long, just long enough to entangle.

Formed-in-place polyurethane works the same way. You have a toxic "A" part and "B" part that react to form a non-toxic long-chain molecule that is very strong and tough. (you're not interested in those properties in foam, but I work a lot with polyurethane paints, and if water contacts it before it cures, it will foam up).

If properly mixed, the isocyanates will be 100% consumed. The only way that doesn't happen is if

• The person used too much B-part, either by accident or on purpose because of a misunderstanding of how polyurethane works.
• The person didn't blend/mix enough, and so inside the bucket are zones too rich in B-part.

If the stuff is turning to powder, that raises some serious questions about whether it was mixed properly. It might be worth obtaining a small amount of it and intentionally mixing it with too much "B" part and see if that makes it behave like yours. If so, I'd consider lawyering up and going after the installer for the health problems.

What isocyanate does

Read the MSDS and the CDC page, but isocyanate is an immune system irritant that can cause anything from "allergy to isocyanates" to some real immune system damage if you get a major slug of it.

However, as the CDC page discusses, isocyanate is very chemically aggressive so it is also very short-lived in the environment. It really wants to hook onto "A-parts" and will grab almost anything, including water vapor. So the isocyanates should have entirely reacted within a week or so. It's not a vapor itself, so it won't waft down.

But if you were exposed to a lot of it due to improper mixing, that might have done some damage.

But otherwise, any long-term health problems must be caused by other chemicals - the isocyanate is gone now.

What to do about it

Don't fall into the trap of "doing what is easy instead of what is effective". If you want to stop being sick, you need to do what it takes. You alone must decide what your health is worth.

So it sounds like somebody chiseled out the bulk of the foam material. But I presume a lot of it was in direct contact with the wood, and I gather the part touching the wood is still there.

Well, that's not good enough. You will need to encapsulate it.

• First, remove all the material you can. I would use a wire-brush or whatever else works. Use a shop-vac that has a HEPA filter so you aren't spreading it around even more. Wear a dust mask yourself, preferably an N95 if you can obtain one during the pandemic.
• Then, with dust removed and after a water wipe-down and letting that dry, seal the surfaces with a primer. Now my favorite primer is - ironically - a 2-part epoxy, but it is VERY fumey. My second go-to is KILZ Original, but that is also quite fumey, being an alkyd primer. So to minimize environmental sensitivity I'd use KILZ 2 preferably in a low-VOC form.
• Prime all surfaces that ever had foam. I recommend 2 coats, and in any case use all the paint. Never keep old latex paint around - now with the low-VOC requirements it is very susceptible to mold and fungus - and if you think you have problems now, try stopping the foul stench of moldy paint!

You'd be working in the attic a lot. I gather it doesn't have floorboards. Take some plywood sheets up there (cut them down as needed to bring up there) and screw them down temporarily so you have a comfortable work area and aren't having to play Spider-man across the joists carrying tools and vacuums.