There would need to be Industrial Strength Mouthwash made available {without delay!} to each patient while undergoing this breathing therapy. How flammable is methane anyway?
Some may need to approach their cigarette smoking with new caution.
The old Listerine Mouth wash probably saved the lives of a lot people during the 1918 epidemic.
It is still available and on the shelves of most drug stores and many grocery stores.