Air Admittance Valves от IPS Corporation

The Studor AAV can be used in lieu of expensive and complex plumbing (open pipe) vent systems that penetrate roofs of buildings.
The purpose of vents is to allow air to enter the plumbing drainage waste and vent system and equalize pressure when water drains out of the system maintaining the integrity of the water trap that prevents sewer gases from entering the building through fixture drains.