What type of appliance requires a flue or vent?

A flue or vent is necessary for gas appliances that produce combustion gases because these appliances burn fuel (such as natural gas or propane) to generate heat. During the combustion process, various gases, including carbon monoxide, are produced as byproducts. To ensure safe operation and to prevent the buildup of harmful gases inside a building, a flue or vent system is installed. This system directs the combustion gases outside, away from living spaces, thus protecting occupant health and safety.

Electric heaters do not produce combustion gases since they generate heat through electrical resistance, making a flue unnecessary. Non-combustible appliances do not ignite fuel or require venting of combustion gases since they do not burn a fuel source. Portable gas stoves, while they do produce combustion gases, can sometimes operate safely indoors without extensive venting under certain conditions, though it is still advisable to use them in well-ventilated areas. Therefore, gas appliances that produce combustion gases are the primary equipment that mandates a flue or vent for proper exhaust and safety.