What is a Chimney Pipe? What is a Chimney Pipe?

With two primary types, a chimney pipe is a metal tube used as a means of ventilation. They are necessary with indoor appliances that use some form of combustion to produce heat, whether it is the burning of wood, gas, oil or coal. Appliances that have chimney pipes as one of their components include certain stoves, fireplaces, boilers, water heaters and chimneys. The two basic types of chimney pipe are known as Class A and Class B pipes. Class A pipes simply vent exhaust while Class B pipes possess both an intake and an exhaust mechanism. 

How a Chimney Pipe Works

A chimney pipe attaches to the top or side of the appliance to be vented. For smaller appliances requiring a pipe, it is most commonly a cylindrical tube that vents the exhaust out of the home or building. While the fastest way to vent is a straight tube, at times it is necessary to shape the pipe in a particular way to get around obstacles, through walls or out the roof. Because of this, chimney pipes are connectable in a variety of ways. Much like metal gutters and downspouts, there are elbow and other angled joints to facilitate directional changes. 

When a Chimney Pipe Is Necessary

In any appliance that combusts fuel to produce heat for warmth, for cooking or to boil water, a certifiable chimney pipe is necessary. Without such a pipe, the interior atmosphere of a home or building would quickly become inundated with exhaust fumes, endangering the inhabitants. Depending on what is combusted and exhausted through the pipe, different levels of pipe insulation may be required, which in turn requires different types of metal to be used. 

Chimney Pipe inside a Chimney

What is customarily thought of as a chimney is actually a masonry structure built around an internal chimney pipe that vents the firebox. This is also known as a chimney liner. When you burn wood in your fireplace, the exhaust escapes through the flue door and out the liner. Likewise, a freestanding wood-burning fireplace has a chimney pipe that performs the same function. It radiates heat while allowing the smoke to vent up and out through the chimney pipe. 

Class A vs. Class B Chimney Pipes

Class A chimney pipes comprise the majority of basic venting pipes for internal appliances. Whatever the fuel is being burned, Class A chimney pipes provide the ventilation. Class B chimney pipes are used specifically with gas-burning stoves or heaters. Outside air is sucked into the gas-burning chamber to add fuel to the fire. The exhaust is then expelled back out into the air. This process is simultaneous and thus requires special gas vent piping. 

Chimney pipe is rated according to the type of fuel combusted. While oil, coal and wood-burning appliances requires the basic Class A chimney pipe, corn and/or pellet-burning appliances call for a different venting system. Chimney pipe must be properly installed and sealed to an appliance in order to ensure safe ventilation, especially when it comes to gas. Considering that natural gas is odorless, any leaks can be deadly. Installation requires professional knowledge and skill, because the utmost care should be taken when venting fuel-burning appliances.

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