3 Causes of Excess Soot in a Gas Fireplace

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One of the most attractive features of gas fireplaces is the fact that they produce relatively little soot and smoke compared to their wood-burning relatives. In fact, with regular maintenance efforts, you can keep your gas fireplace more or less completely soot-free. Yet from time to time, a gas fireplace may produce excessive amounts of soot.

This soot not only mars the appearance of the fireplace, but it also signals a potential health risk since soot almost always occurs in conjunction with carbon monoxide. Homeowners should always contact a professional when their gas fireplace begins to produce soot. Learn about three potential causes of this unwanted phenomenon.

1. Rich Air-Fuel Mix

Soot consists of bits of uncombusted carbon released from the natural gas. When natural gas combusts under perfect circumstances, it produces virtually no soot at all. Instead, soot only occurs when combustion does not occur completely.

The key consideration when it comes to combustion efficiency lies in the air-fuel ratio. In order for the gas to release all of its energy through combustion, it must mix with an appropriate amount of air. When too little air enters the combustion chamber, all of the gas present will not combust. This scenario goes by the name of rich fuel.

Many gas fireplaces – especially those that contain fake logs – deliberately create rich-fuel environments. Although rich fuel produces less heat, and more soot, its flames also have a yellow or orange color more evocative of a wood fire. By contrast, when the air-fuel ratio falls within acceptable limits, the resulting flame will have a blue color.

If you own a gas fireplace designed to produce yellow flame, a contractor may be able to reduce the amount of soot produced by altering your air-fuel ratio. If your fireplace only recently began exhibiting yellow flames or high soot levels, it may need to have its air intake shutters cleaned.

Over time, air intake shutters often become clogged with things like pet hair, dirt, lint, and other household debris. A technician can often reduce soot levels simply by cleaning out the air intake shutters and restoring the air-fuel ratio.

2. Excessive Flame Impingement

Gas fireplaces that contain ceramic logs used to mimic the look of a wood-burning fireplace often fall prey to another problem having to do with flame impingement. Flame impingement simply refers to the fact that the logs naturally come into contact with the burner’s flames. This contact further enhances the illusion that the logs are burning.
In most such fireplaces, homeowners can reposition the logs to suit their taste. Yet if somebody positions a log so that it disrupts a flame too greatly, it may have a detrimental impact on combustion. As a result, the excessively impinged flame produces a much greater amount of soot than it should.

3. Clogged Burner Ports

The flames in a gas fireplace come out of a series of burner ports, each of which allows a small stream of gas to flow up into the combustion area. The burner ports have relatively small diameters, which makes them susceptible to becoming clogged up with debris. Dirt, dust, insects, and even broken-down bits of ceramic logs can interrupt the flow of gas from a given burner port.

In some cases, such restrictions prevent the burner port from generating flame at all. In other cases, the restriction alters the air-fuel ratio of that particular port. As a result, clogged burner ports may produce excessive levels of soot. To have your burner ports restored to their normal functioning, please contact our team of knowledgeable gas fireplace experts at Alpine Fireplaces.

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