In addition, plumbing vents allow sewer gases to be exhausted outdoors.

The venting system, or plumbing vents, consists of pipes leading from waste pipes to the outdoors, usually through the roof.

Blocked plumbing vents, typically at the roof, also can cause water seals to fail via siphoning of the water.

With properly installed plumbing, the traps will prevent the smoke from entering the house and redirect it out the plumbing vents.

Plumes coming from plumbing vents or the interface between the fan shroud and manhole rim are normal; however, smoke plumes outside of the manhole rim are not.

In buildings with HVAC air handlers that admit outside air for ventilation, plumbing vents placed too closely to air intakes or windows can be a source of sewer gas odors.

For example, pollutants from motor vehicle exhausts; plumbing vents, and building exhausts (e.g., bathrooms and kitchens) can enter the building through poorly located air intake vents, windows, and other openings.