This large air convection currents experiment apparatus allows students to see normally invisible air convection currents in action and understand how hot and cold air make the current flow. Air, heated by a candle (included), moves up one chimney, while cooler air moves down the other chimney to replace the lost air. A smoke-producing stick such as incense (included) makes this air motion visible to students. The air convection currents experiment kit includes a metal box with a glass front for easy viewing, two chimneys and a candle. Metal Box Dimensions (lxwxh): 8.5" x 4" x 4" Chimney Length: 6" Included: Candle, Incense Sticks