How To Vent A Gas Fireplace [4 Options]

When you decide to purchase a gas fireplace, one of the first things you need to figure out is how to vent it safely. Depending on what kind of fireplace you choose, if you’re building your home or remodeling, it’s relatively easy to run venting through the wall, through the roof, or even directly into the chimney. But if you’re buying an existing home with an existing fireplace and need to connect your new gas fireplace system, things can get a little more complicated.

A gas fireplace can be vented through the chimney, directly through the wall (horizontally), or through the roof (vertically). Gas fireplaces’ less common venting methods include a natural vent or power vent, while vent-free fireplaces also exist that don’t require any venting system.

Venting your gas fireplace may seem like a simple process, but there are several options available to you that have their advantages and disadvantages. Each option requires a type of vent pipe, which you can find at most hardware stores or fireplace supply centers. In this guide, I’ll go over the different types of gas fireplace vents and what kind of venting system each one requires.

How does a gas fireplace work?

A gas fireplace operates on gas and is fitted with a burner and a venting system. A gas fireplace offers many of the same benefits as other fireplaces. It gives off both ambiance and heat comfort when it’s cold outside.

It works differently from traditional fireplaces that burn wood as it doesn’t necessarily require a chimney to eliminate the fumes. It uses a pipe venting system that throws the exhaust to the exterior. The glass panel in front of the gas fireplace makes it safe by preventing access to the fire.

A gas fireplace
A gas fireplace

Do you need ventilation for a gas fireplace?

Before venting your gas fireplace, first determine if you need ventilation for it. Unless it’s a vent-free fireplace, you’ll need a venting system. Gas combustion produces exhaust fumes and carbon monoxide, so proper ventilation is necessary for a gas fireplace. In rare cases, some gas fireplaces don’t have access to chimneys and must be vented through another route. It can be done through an exterior wall or the roof. Consult with a professional before trying to install vents yourself. It’s not easy and should only be done by someone who knows what they’re doing.

Which is better ventless or vented gas fireplace?

Since ventless gas fireplaces burn with an invisible flame, they don’t require any special ventilation, making them an ideal choice if you cannot be bothered to vent your fireplace. However, since they do produce some visible smoke and exhaust, it’s best to install your fireplace in an area that is not too confined. However, it’s no contest for heat output and efficiency—vented gas fireplaces blow away their ventless counterparts.

How to vent a gas fireplace without a chimney?

Here are four types of venting options for a gas fireplace that don’t require a chimney:

1. Direct vent fireplace venting

Gas fireplaces with direct venting are the safest choice because they throw out combustion fumes and pollutants through a small hole in the exterior wall or a chimney (optional). Homeowners can enjoy a comfortable heated environment without fear of breathing in unhealthy emissions. Direct vent fireplaces are usually lined with glass panes at the front, so they are safe, efficient, and versatile options for supplementary heat and can be placed almost anywhere. Direct-vent fireplaces tend to be about 70%-85% efficient. Direct-vent fireplaces are ideal for new and more airtight homes.

How does it work?

A direct-vent fireplace draws in fresh air from outside into the unit for combustion, and a flue system expels the exhaust to the outside. Most direct-vent fireplaces have two venting options:

  1. Through the wall or horizontal direct vent
  2. Through the roof or vertical direct vent

A pair of rigid flues called coaxial units is used for venting the fireplace. These flues are fitted into each other using a common axis. The inner flue is 4″ in diameter that is surrounded by an outer flue with a diameter of 6 5/8” or 8”. They are installed in sections that are from 4” up to 48” in length and are paired with angled elbows of 90 degrees or 45 degrees for ease in placement.

The exhaust is vented outside through the inner pipe when you start the gas fireplace. On the other hand, the outer pipe brings in fresh air for combustion directly into the bottom of the airtight firebox and ignites the fireplace. The high-temperature glass panel of the fireplace is completely sealed off to keep combustible byproducts and flames from entering the home’s clean breathing air. Also, it doesn’t take any air from home for combustion. The fireplace draws in air and throws out fumes through the direct-vent pipe.

The direct-vent fireplaces produce efficient heat and are available in different sizes. The best part is that they don’t require a chimney and can be installed in any home and interior.

A) Through the wall or horizontal direct vent

It is an ideal venting solution when the fireplace is installed against an exterior wall. Horizontal venting is the easiest option in such a case because you only have to insert a pipe from the back of the fireplace through the wall to the exterior and install a termination cap on it. Venting through the wall doesn’t require extensive work, saving time and installation costs.

The key consideration in venting through the wall is deciding where to place the termination cap and the height of the termination vent. You will not want to put it on your patio or deck because it gives out noises from cap filling and throws out combustion fumes into that area. Also, make sure that snow doesn’t fall directly onto the cap and render it useless.

Direct vent installation

B) Through the roof or vertical direct vent

Venting through the roof is costly and labor-intensive work, but sometimes it’s the only option or a practical option. For example, if the fireplace is installed on an interior wall, then venting through the exterior wall is not possible, and your only option is to vent through the roof. Sometimes, a chimney is already available to run the venting through it to the roof.

2. Natural Venting

A natural vent or B-vent draws air for combustion from indoors and throws out exhaust fumes via a chimney or venting system using pipes going through the roof. A few fireplaces with natural venting come with sensors to stop the fire if exhaust fails and gases return to the flue.

However, natural vent fireplaces are not very efficient in providing heat, although they produce a stunning flame pattern. On the other hand, they are more flexible with running the vent pipe and are cheaper to install. Also, they are more responsive to indoor airflow despite being cheaper.

Some of the advantages of installing a B-vent gas fireplace are:

  • People prefer to have B-vent appliances as they comply with local building regulations. They produce less harmful exhaust as compared to wood-burning fireplaces so B-vent gas fireplaces are a more environmental-friendly option.
  • B-vent is smaller in size so doesn’t require large clearance in the chimney or otherwise. Therefore, it is a perfect pick for house remodeling because of its easy installation.
  • Even though they don’t produce as much heat as direct vent fireplaces, they are certainly more efficient than vent-free fireplaces.
  • B-vent fireplaces look more comforting as their large and beautiful flames give an illusion of more heat while looking like real flames.
B-vent vs direct vent for gas furnaces

3. Vent-free fireplaces

The easiest way to vent a gas fireplace is when you don’t have to vent the fireplace. Opt for a vent-free fireplace to avoid all the hassle of finding a venting option for your gas fireplace. You’ll not need any chimney, vent pipe system, or venting to get rid of gas fumes. The vent-free option gives you the flexibility of installing the fireplace anywhere in the house.

Moreover, there are some specific situations where going vent-free is your only solution. Suppose you want to install a fireplace against an interior wall, but you don’t have a chimney available to run the vent through it, and you don’t want to invest in venting through the roof. The most feasible option is to buy a vent-free fireplace in such a scenario. Vent-free fireplaces run on propane or gas, so you’ll need to hire a professional plumber to install a gas or propane line, and you’ll be set.

This section is not complete without mentioning that the exhaust fumes are being released into your home by a vent-free gas fireplace. Many such fireplaces come with a carbon monoxide monitor and oxygen level alert system, but I recommend having a second monitor to ensure more safety. Also, you’ll need to have a vent-free gas fireplace cleaned and checked annually by a professional company to ensure it is in safe working condition.

4. Power venting

This venting option uses a fixture powered by a fan with the vent to facilitate the airflow. It enhances the performance of a direct vent fireplace if the existing venting system is not moving adequate airflow to the fire, or it can also be used to vent down a fireplace. There are two options to put this fan-powered device, either on the venting or outside the termination cap. It allows flexible venting to go up and down so the fireplace can be installed anywhere. It provides a safe gas fireplace with the best flames.

Power venting a fireplace

EPA Recommendation for using a gas fireplace without a chimney

Environmental Protection Agency recommends following some specific guidelines if you plan to install a gas fireplace using a method other than a chimney. These guidelines are for the protection and safety of you and the people living near you, so follow them completely to get the best out of your gas fireplace.

I have included these recommendations only for reference, and I strongly suggest that you go through the manufacturer’s manual for complete information on EPA recommendations.

  • The first thing EPA recommends is contacting your local authority to have your gas pipelines checked before installing a gas fireplace. They have all the information about the types of the vent and the right way to use them. Ask them for advice regarding qualified professionals to handle your installation and venting needs.
  • It is also advised to contact your gas-providing company to ensure that you are doing everything right. They will also tell you if there are any restraints on which carbon monoxide vents need to be used.
  • You also need to use a flue damper in the chimney-like structure of the vent so cold air cannot enter the house via any open gaps in the vent. You have to check it periodically if it is not blocking out the exhaust from escaping which can result in poisoning the air with carbon monoxide.
  • Another important thing to consider is that the exhaust pipe running through the outside wall should be a minimum of three feet distance from any doors or windows, so it doesn’t cause any air draft issues inside the home.
  • Lastly, don’t forget to fit the propane hose to the exhaust pipe bottom with the help of a metal band or rubber clamp.

Frequently Asked Questions

Are direct-vent gas fireplaces safe?

Direct-vent fireplaces are an efficient way of heating your home’s interior without electricity. They have an airtight combustion chamber for fire and a direct vent that gets rid of unhealthy combustion products directly through the back wall or the roof. The glass panel makes them a safe heating source in houses with small children and pets. Direct-vent fireplaces provide a safe option for venting if you don’t have a chimney in your house.

Which one is better B vent or direct vent gas fireplace?

B Vent and Direct Vent gas fireplaces both are attractive, efficient, and cost-effective ways to heat your home. Choosing between a B vent and a direct vent gas fireplace can be difficult. After all, each style has its benefits and drawbacks depending on the location where you want to install the fireplace. Depending on popularity you can see that mostly direct vent gas fireplaces are the first choice for most homeowners. However, look at all the possibilities, weigh the pros and cons of both models and then pick which one ticks more boxes for you.

How long can you run a vented gas fireplace?

Vented gas fireplaces can be operated safely in your home, knowing that the exhaust fumes are not entering your home’s space. But take some precautions to be on the safe side and not run your gas fireplace for more than 3 hours at a stretch. If you’re trying to save money on heating bills, it is important to check with a professional for advice on the best practices of using a gas fireplace.

How can I tell if my gas fireplace is vented?

A gas fireplace replicates the appearance of a real wood fire, so if you observe that the flames are not looking as real, there is a problem with your gas fireplace venting. A properly vented gas fireplace will show eye-catching orange and yellow flames that are big and straight up at the edges of ceramic logs. 

On the other hand, improper venting will result in unattractive flames that are smaller and bluish. The other tell-tale sign of the gas fireplace’s improper venting is the interior of your home feels too hot. Gas fireplaces are not extremely efficient in producing heat when vented, so overheating should be of concern.

What happens if I don’t vent my gas fireplace?

A gas fireplace needs to be vented unless it is a ventless fireplace. Carbon monoxide and other poisonous gases can sneak into your living space if a gas fireplace isn’t properly vented. Even small amounts of these harmful gases can have serious long-term health consequences. If you have a vent-free gas fireplace, it is extremely important to check for leaks around your home regularly. Carbon monoxide detectors are strongly recommended for every household; they’re inexpensive and save lives. 

How can I make my gas fireplace vent more efficient?

It’s important to remember that hot air rises, so most of it escapes through the vent. Gas fireplaces also create an updraft while operating that can suck the warm air out of your home, affecting the efficiency of the fireplace. Using a flue damper can prevent the hot air from escaping out, and it also fulfills EPA’s recommendations, so it’s a win-win situation.


If you are installing a gas fireplace in your home, you must consider your location and proximity to other structures and the venting options. A vented gas fireplace is an important safety feature as it allows heat and gases to escape your house, ensuring proper combustion and carbon monoxide build-up. 

I hope this article has provided valuable information that will help you choose a suitable venting option for your gas fireplace. If you have learned something you didn’t know before, or you have discovered that one type of gas fireplace venting better suits your needs than the other, don’t hesitate to share your information with an expert and ask for their advice before making a final decision.

Charles John

A novice DIYer who learns about home ventilation. I am a mechanical engineer and have a basic knowledge of HVAC systems but I learn continuously to make myself the best blogger in that space.

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