I've applied two coats of Helmsman spar urethane over the original polyurethane finish that has been on the white pine interior of my sauna for years. After a month of heating the room and running a box fan, my son's asthma flares as soon as he goes inside. Checked with Minwax and they said it would never cure and be safe for anyone in this setting and that I should remove it and find something different which will be a huge task (it's on walls, ceiling & benches). Is there something safe that I could apply over it that would encapsulate it? If not, how best can I remove it and what would be a proper finish that can handle the water and temps to 200 degrees. Would a heat gun and scraper be best? A company in the UK offers a couple of finishes made specifically for saunas but I don't see anything in the US.