How Does a Fireplace Work?

Combustion Air

A fireplace needs combustion air or constant airflow and fuel in order to work. The air rises and escapes through the chimney when heated by fire. This happens when the air inside the chimney gets warmer and less dense compared to the air outside the chimney. Cooler air flows into the firebox that fans the fire whenever the warm air rises up, producing more heat in an ongoing cycle.

Gas Fireplaces

Gas fireplaces make use of ceramic logs and a burner to produce a glowing flame powered by natural gas. They come in three different styles: the direct vent, the top vent design and the vent-free model.

There are two pipes in a direct vent fireplace leading outdoors. One is for combustion air and another for the exhaust gas. The top vent gas fireplace makes use of metal or brick chimney as the exhaust vent. The source of the combustion air for the top vent design comes from inside the house. Finally, the vent-free gas fireplace does not use any exhaust vent. Instead, it uses an oxygen-depletion sensor that turns off automatically after sensing lack of oxygen inside the house.

Wood Stove

A wood stove comes in different shapes and sizes. It comes in a metal container usually made with cast irons or welded steel. A wood stove uses an inlet for combustion air and an outlet for smoke or combustion gas. The wood stove burns wood to produce heat. It provides more heat and burns better than a traditional open fireplace because of its airtight features that allow well-controlled feeds of combustion air. It can convert up to 90 percent of their fuel to heat making it more efficient.

With its improved designs, a new certified wood stove only gives off about 5 grams of particulate emissions per hour of smoke compared to 50 grams on older wood stoves. This improvement addresses the concerns about the dangerous or toxic gases carried by wood smoke.

Zero-clearance Fireplaces

Zero-clearance fireplaces are highly-insulated and come in pre-fabricated form. The fireplaces do not need much space between them and any combustible materials, such as wall frames. They can go as close as 1-inch away from combustible materials without raising concerns of fire hazards. Newly-constructed homes often come with zero-clearance fireplaces because of ease of installation compared to the traditional type of fireplaces. They are also lightweight and more energy-efficient compared to the masonry type fireplaces.