Back in the woods behind a country church, I came across an outhouse with an innovation: Wooden ductwork that forms a “T”, leading to the pit and out through two exterior walls. It was clearly meant for ventilation, but without a lid covering the toilet seat, it seemed pointless—sewage odor would just rise out of the pit. And why two exits for the duct? Seemed dumb.
But I know the settlers who built this outhouse weren’t dumb. The dumb ones didn’t make it though the first winter. So I thought some more and figured out how it worked: On a windy day*, air blows through the horizontal duct. When air moves fast, it exerts less pressure than still air. That low pressure would create suction in the vertical duct, suck stinky air out of the pit and exhaust it outside. Bernoulli’s principle applied to poop!
*This is in North Dakota—every day is a windy day.
— Gary Wentz, Editor in Chief