If you get a black light you will see the yellow mold or mold period. It could be in the walls and you would never know it. I don't know anyone who can test for the mold and this illness has taking me down for years soi dont have money to have it tested. You can do a test online that can see if you have mycotoxins in your eyes. You can try it one time for free at vcstest.com u believe. Just look up vcs testing and it will tell you if there is a problem.