We just bought a 21-year-old house. There is a strong chalky smell on the main floor. The basement, crawl space and upstairs bedrooms don't really smell. The worst is the garage. We air it out all day, but after closing windows and doors you can smell it again. There are tiles in the smelly areas. Any chance it is the tiles or the grout? Is there a non-toxic, green sealant one can use on both the tiles and the grout?