I had the exact same issue with a bathroom I had renovated about 5 years ago and it still smells of a very strong chemical smell which I do believe is coming from the grout black grout which still occasionally runs I have black stains in my shower from this grout that still bleeds the color it's almost as if the grout should have been sealed I don't know but it's baffling. And did smell does get very strong in the room in the bathroom when I keep the door closed when I open the door it does help and the smell doesn't seem two be noticeable in the Next Room. Connie