Allllllllright. This is crossing into a territory beyond plumbing. I'll talk to the plumber who will be doing a job in another room about a sewer gas check in the house, and get their professional opinion on whether it's necessary, and I appreciate your concern. Beyond that, I'm not interested in any more of your input at this point, thanks.Sewer gas isn't healthy. If you live with kids and a wife their health would be worth more than removing some drywall.