What Is a Flame Trap?

Mary McMahon
Mary McMahon

A flame trap is a safety feature which is designed to prevent fire from reaching a fuel supply line. This reduces the risk of explosion or fire, making the system safer to operate. Flame traps are used in a wide variety of systems in an assortment of settings, and on systems which use them, it is important to make sure that they are kept clean and clear so that they will continue to function properly.

Flame traps are a safety feature used with natural gas appliances.
Flame traps are a safety feature used with natural gas appliances.

With a trap, if flames or sparks from the system start to make their way into a dangerous area, such as the supply line, they hit the trap first. The flame trap extinguishes the fire, ensuring that it cannot come into contact with the raw fuel supply. These traps are used on internal combustion engines, lines for fuel gas such as those which supply heaters and stoves, exhaust systems, and other types of equipment which rely on combustion for heat or energy.

A common spot for a flame trap is near an engine.
A common spot for a flame trap is near an engine.

Over time, a flame trap can become clogged with particulates and other material. Byproducts of combustion can build up inside the trap, slowly clogging it. The trap may still be able to extinguish flame, but the flow through the system will be impeded. If it is clogged enough, it can actually create a fire hazard, as the particulates may catch fire. For this reason, traps should be on a regular maintenance checklist so that people can confirm that they are in good working condition.

Cleaning a flame trap varies in difficulty. Some are very accessible and designed for easy cleaning, usually because they need to be cleaned frequently. Others may be harder to reach, and sometimes require the attention of a professional such as a mechanic who is familiar with the system in question. A common spot for a trap is near an engine, and the device is usually labeled on schematic drawings of the system for convenience.

In cases where the trap becomes too clogged or damaged for repair, it will be necessary to replace it. It is important to buy a trap which is designed to work with the system in question, whether it is purchased through a hardware, gas supply, or auto supply store. The flame trap should be installed carefully to make sure that it will work properly and efficiently. People who are not comfortable with handling repairs of this type should hire someone to install the replacement.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


Does anyone know where the flame trap is located on a Volvo 240? I bought a classic Volvo with a great body, but it had blown seals. A friend told me that it was probably due to a dirty flame trap. We looked for about an hour to try to find the flame trap, but we could not locate it.

I have heard it is hard to find (clerk at the parts store), but the person who told me that did not know where to find it. He did try to sell me a flame trap relocation kit, but I am not going to buy it until I can find it and see if it is worthwhile...or if it even has one for that matter.


@georgesplane- Another place where you will find flame arresters in use are on gas powered marine craft. Gas powered marine vehicles are required by the United States Coast Guard to be fitted with flame arresters. In marine applications, I am pretty sure that the flame arrester is located on the air intake. I think it is between the air intake and the engine.


@highlighter- You really only see flame arrestors on vehicles that were manufactured before catalytic converters. For the most part, catalytic converters act as flame traps on naturally aspirated vehicles. Turbo charged vehicles actually use the turbo as a flame trap. Modern automobiles have fuel and air ratios calibrated by computers so the risk of damaging backfires is almost nil.

The only instance where I know of a modern vehicle using a flame trap is in a fuel refinery setting. If I am not mistaken, all vehicles entering a fuel refinery need to have flame arrestors installed to prevent backfires that could cause a disastrous fire. I am not sure if turbocharged diesel trucks need flame arrestors installed, but I would assume that these vehicles would not need one.


Where is the flame arrester in an automobile? Do mechanics refer to them as flame arresters or do mechanics call them something else?

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