Flue On A Gas Fireplace; Should It Be Open?

Fireplaces, and especially the gas ones, usually seem like pretty simple devices. You just turn it on and enjoy the heat. But all the smoke and ash needs to go somewhere, and this is where the flue comes in. But should you have your flue open on your gas fireplace?

The flue of your gas fireplace should be open during and slightly after lighting your pilot light. An open flue ensures proper ventilation, which takes away many safety risks. If the ember bed is completely off, the flue can be closed to retain heat, but otherwise, it should be open.

There are several different scenarios in which your gas fireplace may have a certain type of flue, or in some cases may not even need one at all. This said, the majority of gas fireplaces will have a flue, out of necessity, so keep reading to become an expert on all things flue!

Should You Open The Flue On A Gas Fireplace?

Flues should always be kept open since they’re responsible for ventilating your fireplace. Closing the flue while lighting a fire will push all the smoke and fumes inside your home, so always keep it open, especially if you often light a fire.

The only exception to this is if you have ventless gas logs, which are specifically designed to burn gas cleanly with minimal exhaust.

Keeping your flue open at all times is definitely recommended, but we realize that always keeping your flue open is almost like a small hole in your roof. So, if you want to close your flue, that’s fine, but make sure all your embers are finished burning.

If there’s still something burning, it still produces smoke and fumes, and you don’t want those in your home. If all embers are done burning, though, it’s perfectly safe to close your flue.

Closing the flue will improve the heat retention, as there’s no airway to the outside anymore. This leads to both the heat from your home-heating system staying inside, as well as the heat still coming from your fireplace. Both will be capsulated inside your home, leading to a warmer room.

This also helps with saving money on heating expenses!

Another way to capture the heat inside the fireplace is by closing the doors of your fireplace. This way, you can leave the flue open, but the airway is still cut off.

While keeping your flue closed during periods of non-use will help retain heat, keeping your damper closed while your fireplace is in use will not help your gas logs emit more heat – gas fireplaces are more atmospheric than intended sources of heat.

Related article: Can A Flue Catch Fire?

What Is A Flue?

The flue is where the smoke escapes while a fire is burning, and inside the flue is the damper for your fireplace. In turn, the damper is the vent that controls the air movement in and out of your chimney.

A flue is an important part, and usually, every fireplace/appliance has its own flue. It basically leads the smoke away from your home, into your chimney.

How Do You Open The Flue On A Gas Fireplace

Now that you know your flue needs to be open, you’re probably wondering how to even open it. But before we get into that, you should check whether or not your flue is already open or not. Here’s how to do that:

  • Is there a draft? If the flue is open, and you place your hand above the fireplace, you should be able to feel a breeze from your chimney.
  • What do you see? A bit more effort, but grab a flashlight and take a look up your chimney; if you see a barrier above you, the damper in your flue is closed. If you can see upwards, the flue is open.
  • Is there smoke? A simple way to tell is by lighting your fireplace; if there is an unusual amount of smoke entering your house, your flue is closed and obstructing ventilation. If open, smoke will instead leave through the chimney. This should be done carefully though, preferably with a small fire, as you don’t want to smoke everyone out of the house.

Now you know if your flue is open or not, here is how to open it if necessary. There are several styles of flue fittings, so check to see which controls you have:

  • Metal rod: This is a traditional damper, and the rod will have a push or lift function. Either way, push/ lift as far as you can to open the flue.
  • Rotary knob: Turn the knob as far clockwise as you can to open.
  • Metal chain: This is a top-mount flue, and you’ll want to pull down on the chain. If you pull down and the chain springs back up – the flue is already open.

Do All Gas Fireplaces Have A Flue?

Most gas fireplaces have a flue, as in most states, it’s a required fail-safe mechanism. Flues ventilate the fireplace, ensuring none of the smoke and fumes enter your home. Many models nowadays also contain a keep-open device that makes it so the flue never fully closes and always functions correctly.

There are several types of gas fireplaces, and you will definitely have a flue if you have either a direct or natural-vent gas fireplace.

  • Direct vent gas fireplaces

These need a flue and damper system to function, allowing air to be vented between your fireplace and outside. This prevents waste air from mixing with the air you breathe.

  • Natural vent gas fireplaces

These use chimneys as a method for drafting smoke outside and typically sit within masonry fireplaces. It’s standard for natural vents to always be open, thus not necessarily needing a damper inside the flue – however, if they do have a damper, they should always be left open inside the chimney.

The last scenario is that you have a ventless/ flueless/ vent-free gas fireplace, which by design is safe to operate indoors without the need for the ventilation provided by a flue.

This is because they burn gas so cleanly that there is no carbon monoxide, produced, and instead only carbon dioxide and water vapor. Sometimes an external air vent can be useful with these to ensure adequate oxygen levels. Ventless fireplaces are more versatile as can be placed anywhere in the house, without the need for the flue.

Dan Westfield

Hi everyone! My name is Dan and I currently have two fireplaces, a wood-burning and a gas one. I cannot live without them and love to share my passion with you all!

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