When right-clicked with an item or filled with a hopper, the chimney keeps the item and then sends it towards its sink. If the sink is air, the item is dropped here; if connected to a container, the item goes into it; otherwise the chimney is blocked and then blocks the hopper or chimney above it (if any). To put items in by right-clicking, the block above the chimney must be air.

A smoking chimney goes sooty faster if items go through often (can be prevented by a redstone signal, a hopper above it also prevents smoking), and putting an item into a sooty one blocks it immediately (unblock it by using axe, or just mine it to get the item back).

Food items can be cooked by going through smoking chimney pipe that is long enough.