The 360 Siphon RV holding tank vent cap eliminates odors from the source - the holding tanks - and exhausts them out the roof vent before they have a chance to invade the RV living space. By design, the patented 360 Siphon can only create an updraft, expelling odors and fostering an oxygen-rich environment to speed up waste breakdown. Breathe easier and enjoy a healthy, odor-free living environment with the 360 Siphon.