What device prevents sewer gas from entering a room containing plumbing fixtures?

The device that prevents sewer gas from entering a room containing plumbing fixtures is a trap. A trap is specifically designed to hold a small amount of water, creating a seal that acts as a barrier against the passage of gases from the sewer system. When water flows through the plumbing fixture, it fills the trap, which then prevents odors and gases from escaping into living spaces.

Traps are critical components of plumbing systems, particularly under sinks, toilets, and other fixtures, as they not only keep unpleasant sewer gas from entering the home but also maintain a continuous flow of water that can help to prevent clogging. In some cases, traps must be periodically cleaned and maintained to ensure they function effectively, as build-up can impair their ability to provide that essential seal.

In contrast, while vents facilitate air circulation within the plumbing system to maintain siphon levels and enhance drainage, they are not specifically designed to block sewer gases. Valves control the flow and pressure of liquids but do not address gas separation, and filters are used in various contexts for cleaning air or liquids but do not serve the function of preventing gas entry from sewer systems.