I am buying a house and the home inspector stated
"Improperly sloped vent pipe noted. This will allow
products of combustion to escape. This is a safety hazard
needing immediate attention by a licensed heating contractor"
Is an incorrectly sloped vent dangerous?
That is why there's a code dealing with vent slopes. Hot air rises so if the flue is sloped the wrong way then the combustion byproducts,including carbon monoxide, spill into the house. When that happens you get sick because your internal organs are shutting down from lack of oxygen,or you just up and die.