National Home Inspector Practice Exam 2025 - Free Home Inspector Practice Questions and Study Guide

The feature that helps prevent sewer gas from entering a home is the traps in drains. Traps are plumbing fittings that are designed to hold a small amount of water at all times. This water creates a seal between the sewer line and the home, effectively blocking odors and gases from the sewage system from rising up into the living space.

Traps are strategically placed in various plumbing fixtures such as sinks, toilets, and bathtubs. When water flows through these fixtures, it fills the trap and maintains the water barrier. If the trap were to dry out (for instance, in an unused drain), it would no longer provide that necessary barrier, allowing sewer gas to escape into the home.

While exhaust vents are crucial for allowing ventilation in areas like bathrooms and kitchens, they do not specifically prevent sewer gas from penetrating the living space. Air filters and dehumidifiers, while essential for improving air quality and moisture control indoors, do not address the specific issue of blocking sewer gases. Thus, traps in drains are the most effective feature for this purpose.