Blowdown stack

A blowdown stack is a thing that helps keep air clean. It's a tall pipe that sticks up on the roof of a building, like a hat on a person's head. When people use machines or tools inside the building, they create dirty air that has bad stuff in it that we don't want to breathe. The blowdown stack helps blow all that dirty air outside so it doesn't stay inside and make us sick. It works like blowing out candles on a birthday cake - the air gets blown out of the building and into the sky where it can't harm anyone.