Ensuring that air enters (ventilation) and exits (exhaust) the composting toilet system in the right direction is critical for maintaining the composting toilet system and preventing odors from entering the home.

If your toilet room is on the side of the house opposite the prevailing winds, wind pressure on the windward size of the house pulls a vacuum on the opposite or leeward side. So, when you open your bathroom window on the leeward side, odor will be pulled from your toilet and into the room. You will know that this is the case if the window curtains blow out. If they blow into the room, then the toilet is pressurized, and no odor will come into the room.

This is not as much of a problem with fan-forced ventilation/exhaust systems, because the fan can overcome the negative wind pressure. However, when the fan is off, well, that’s another story. This is not a problem with systems with trap-seal toilets.

Wind turbines work in areas with steady strong winds but according to a National Forest Service study can actually impede air flow at wind speeds of less than 10 to 15 mph.

Instead of the wind turbine, A simple plumbing tee at the top of the pipe both keeps the rain out and provides sufficient venture action effect (whereby wind sucks air out of the pipe).

Sophisticated extractors, such as the Vacu-Stack™ available from wood stove dealers, both keep out the rain and increase the rate of exhaust extraction when wind blows across rigid foils arranged in a globe fashion around the pipe opening.