Which type of fuel burning appliances are permitted to connect to the same flue?

The correct answer is that gas fuel burning appliances are permitted to connect to the same flue. In many jurisdictions, including those governed by the Maine Journeyman Oil Fuel Board Rules, gas appliances are designed with specific venting requirements that allow them to share a flue with other gas appliances when properly configured.

This is primarily because gas appliances produce relatively low amounts of flue gas and generate less creosote compared to solid fuel burning appliances. Additionally, gas appliances often have different temperature and pressure characteristics which can be effectively vented together to ensure proper draft and safety, provided that local codes and manufacturer specifications are adhered to.

Solid fuel burning appliances, such as those using wood or coal, have different combustion characteristics and produce more particulate matter and condensate, which can lead to blockages or build-ups in a shared flue system. For safety and efficiency, these appliances generally require their own dedicated flue to minimize the risk of chimney fires and ensure proper ventilation for each type of appliance. Thus, connecting both solid and gas fuels to the same flue is discouraged to maintain adherence to safety standards and building codes.