I started using Gaco years ago primarily to solve ponding water Problem. It has work well, solved my problems with other roofing options and repairs as well as many other Flat roof issues. My only problems were experienced when I did not clean the surface well enough for good adhesion. Follow the Instructions. Great product and highly recommended. .
If you're chemically sensitive, it's probably not a good idea to get it installed, but it's also not a good idea to breathe musty air from the crawl space either. In addition, your house and its contents are made of lots of materials that affect your indoor air quality. If you're really concerned about this, hire a company to test your air and tell you what you can do about it. http://y2u.be/ggLAUsiuI_o