https://www.yzwc.net/product/floor-drain/ The traditional S-trap or P-trap in a stainless steel floor drain is designed to hold a small amount of water. This water acts as a barrier, preventing sewer gases from rising through the drain and into the room. Some stainless steel floor drains are equipped with built-in ventilation systems that help to expel odors and maintain a fresh environment. These systems work by drawing in fresh air and pushing out stale air, thus reducing the concentration of odors.