Also called Artis Caps, these vacuum chimney caps are used for fossil fuel chimneys and other flue exhaust and are designed to prevent downdraft and/or poor air draws that can be created by wind. This classic design creates a vacuuming effect at it's base that pulls air and fumes out of your chimney. Available with or without spark arresting screen and the sizes below are designed to fit the outer diameter of your chimney pipe. If installing on a square tile or masonry chimney see our adapters HERE