Hi, You will need a tube of approximately 22mm I.D. (internal) this can be secured on to the chimney using a regular hose clip, as the oil is a non-aggressive mineral oil you should be fine with virtually and type of hose, silicone and reinforced PVC hose are the most commonly used. It is also possible, although not ideal, to push a tube with a 20mm O.D. inside the fitting of the exhaust, you absolutely MUST ensure that the tube doesn't slide right to the base (cutting a diagonal on the end helps, or securing ahose clip to act a stop) otherwise the exhaust air with build-up pressure inside the pump and the lid is likely to go pop in a rather explosive manner!