I have many projects that I need to apply finish to. Some I got away with using mineral oil (as that was the intended finish anyways) but others, a table and an acoustic guitar, I need to varnish with a polyurethane varnish.

I have a climate (humidity and temperature) controlled workshop, however it does not have the ventilation that would be required to reasonably finish in, and it's also the air intake for the furnace that supplies the house.

What strategies are there for this? The table is a Christmas gift and must be finished in time, the other does not have a strict schedule but I'd like to be able to finish on my own schedule.

Edit : My main concern here is safely doing this, I have less concerns about the smell, if that's not a serious issue, I can spend most of my time not in the same room and then I'll have no issues