Vent-Guard eliminates vent stack and grease interceptor toxic sewer gases from entering HVAC systems, roof gardens, living areas, pools, windows, skylights etc. The top is infused with Carbon Black, which protects against UV rays. It is a quick, inexpensive and easy alternative to relocating vent stacks or charcoal filter devices that require periodic cleaning and replacement. Vent-Guard’s mushroom-shaped top eliminates insect, animal and inclement weather. Vent-Guard is a push-fit installation into 2, 3 or 4 feet vent stacks.