🔥 The Operation of a Chimney 🔥 Ever wondered how your fireplace keeps the smoke out of your living room? It’s all thanks to the chimney’s natural draft system. When a fire burns, hot gases rise through the flue because they’re lighter than the cooler air outside. This upward movement—called the stack effect—creates a vacuum at the base of the chimney, pulling fresh air into the firebox to keep the flames alive while safely expelling smoke and carbon monoxide. Key parts that make it work: Flue