Flame Roll-Out in a Furnace: What You Need to Know | Peak Home Performance
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Maintaining the safety of our customers is one of our major concerns at Peak Home Performance. Gas furnaces are the residential heating systems that need the most safety attention. This doesn’t mean a gas furnace is automatically a dangerous appliance: if you keep your furnace maintained regularly, you’ll have few safety worries during its lifespan.

However, we want to draw your attention to a specific furnace safety issue that can sometimes occur. Even the best maintenance and the most diligent repairs won’t prevent 100% of furnace malfunctions, such as the topic we’re going to examine today: flame roll-out.

Flame Roll-Out: The Basics

What do you think of when we say “gas furnace dangers”? We’d bet your mind first flashed to carbon monoxide poisoning. That is a major concern, but flame roll-out is an equal one—and an entirely different type of danger. It’s when flames inside the furnace escape from the combustion chamber as they seek to find more oxygen. When a furnace runs normally, the flames from the gas jets remain inside the combustion chamber, their heat drawn upward by the draft inducer into the heat exchanger.

Why might these flames escape from the combustion chamber? There are a couple of potential causes.

First, non-flammable gases can build up in the combustion chamber. These gases will prevent oxygen from reaching the flames, and the oxygen-starved fire will move to wherever there’s oxygen—which often means getting out of the combustion chamber.

Second, the exhaust flue for the furnace may become blocked (this often occurs due to lack of maintenance), which traps the combustion gases in the combustion chamber until they build up into such a high concentration that they’ll escape from the chamber when they finally ignite.

Why This Is a Problem

Flame-roll out is dangerous because you don’t want fire escaping from your furnace. This is one of the reasons we recommend you keep the area around the furnace clear of flammable materials. But even if the flames don’t get out of the furnace, only escaping the combustion chamber, they will severely damage other components in the furnace and cause them to ignite as well. This can lead to the whole furnace catching fire.

How the Furnace Prevents This

Flame roll-out would be a much more common problem with furnaces if not for a specially designed mechanism called the flame roll-out switch. This switch detects when the heat levels outside the combustion chamber rise too high, after which it shuts off the gas flow to the burners. The switch can break, and the danger of flame roll-out is much higher when this happens. (Once again, maintenance is a major help: technicians always check the functionality of the flame roll-out switch.)


As we’ve mentioned above, regular maintenance is your best way to prevent flame roll-out and other safety hazards. Our technicians will check the flame roll-out switch, the combustion chamber, the burners, and the exhaust flue to ensure they’re working right. If you need heater repair in Castle Rock, CO to keep your furnace running safely, we’ll inform you during maintenance so you can schedule the work ASAP.

Rely on the experts at Peak Home Performance: Guaranteed Comfort and Affordability.

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