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A steel flue is a section of steel piping used to vent exhaust gases. Venting is critical to prevent gas buildup, as accumulations of gases can threaten human health, in addition to impairing the function of devices like furnaces and stoves. There are a number of advantages to using a steel flue or a flue liner made from steel, including increased reliability and safety. Many home supply stores carry or can order steel flues, and they can be installed by contractors familiar with the requirements for safe ventilation.
One key advantage to a steel flue is reduced heat transfer. Exhaust gases tend to be very hot, and can potentially start fires if they are vented through a flue that readily transfers the heat. Steel is a poor conductor of heat, especially when it is used in a lined flue, where an air chamber is created between two layers of material, like steel and stone. The heat from the gases will not transfer away from the flue as they are vented, limiting the risk of fires and other problems, such as objects around the flue melting.
In addition, steel resists corrosion. Water and other fluids pouring into the flue will be less likely to damage it, and corrosive byproducts of exhaust will be safely ventilated, rather than damaging the flue. This extends its life and also increases safety, as corrosion can lead to holes where sparks and flammable materials can slip through, potentially starting a fire or creating a hazardous situation.
Building codes usually provide very strict requirements for ventilation around furnaces, heaters, stoves, and so forth. The goal is to prevent safety problems, such as suffocation from collections of gases, health problems caused by inhaling particulates, and fires caused by heated exhaust gases. The code provides requirements for the length and width of flues, along with building materials. Steel is usually permissible and may be strongly recommended in some cases.
Once a steel flue is installed, it needs to be maintained. It is important to periodically clean and inspect it, removing buildups of material and checking for holes, signs of corrosion, and other issues. These problems should be addressed promptly to keep the steel flue safe and operational. Many communities host chimney sweeps and other professionals who are competent at inspecting and maintaining equipment used for venting exhaust gases. People who are renting can ask their landlords about assistance with paying for these inspections if they cannot afford them; landlords are often willing to help because it's in their interests to keep the home or business safe.