360 Siphon Vent Cap by Lippert Components

The 360 Siphon® RV holding tank vent cap remove 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. Even environmentally-friendly tank additives can take up to 48 hours after use to fully oxygenate a standard holding tank. The 360 Siphon acts immediately after installation in any wind condition (with or without a breeze) to provide the ideal environment for proper decomposition, so caustic chemicals and perfumed cover-ups are no longer needed.

[@sporty155]

I disagree, creating an updraft in the pipe will NOT get fresh air all the way into the tank, for that to happen you need another air source feeding directly into the tank independent of the vent pipe. Prove me wrong~