Do you really want to use something cheap in the area where an exhaust leak would be most likely to sicken or kill you?
CO poisioning is insidious, it warps your thinking before you reach the level where you become unconcious (then dead).
We had a friend who got CO in their house when a roofer knocked off the water heater vent. She said she was worried she was becoming mentally ill, as she got forgetful and easily confused.
