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Gas Fireplace Buying Guide

Everything you need to know to choose the right gas fireplace for your home!


There are three main styles of gas fireplaces — Direct VentVentless (Vent-Free), and B-Vent.

Direct Vent fireplaces are the most popular option, while Ventless fireplaces give you flexibility with installation and don’t require a chimney. B-Vent is the least popular, but has the most realistic flame appearance.

If you’re thinking about buying a gas fireplace for your home, read below to find out everything you need to know about how each style works, venting requirements, ideal locations, and the most popular models!



Direct Vent fireplaces are efficient and safe alternatives to traditional gas and wood burning fireplaces.

They don’t require a traditional brick chimney, but instead use a completely sealed venting system to pull fresh outside air into the firebox for combustion, while simultaneously exhausting combustion gases outside of the home.

With a sealed venting system and firebox, Direct Vent fireplaces won’t draw air from inside the home for combustion, nor will combustion byproducts, like carbon monoxide, be able to enter back into the home.

This maintains indoor air quality and protects overall home efficiency while allowing the fireplace to work effectively.


Direct Vent fireplaces can work one of two ways— through a co-linear or co-axial venting system.

Co-Linear Venting

Co-linear systems feature two pipes that run parallel to each other, one to pull in fresh air for combustion, the other to exhaust combustion byproducts.

Co-linear venting is most often used with Direct Vent inserts in masonry chimneys and can only be terminated vertically.

Co-Axial Venting

Co-axial systems consist of a pipe within a pipe, separated by one inch or more. The outer pipe draws in fresh outside air for combustion while the inner pipe expels combustion byproducts.

As the hot air from the fireplace exits the home, cool air is pulled in from outdoors, creating a consistent flow of heat, known as a convection loop.

Heat Circulation

Inside the home, cool air is pulled into the convection air intake on the lower portion of the firebox. The air circulates around the firebox before being released back into the room as hot air. An optional fan, called a blower, is often available to help push more hot air out into the room.

Some fireplaces have the option to have a heat dump system installed, which will pull the heat from the fireplace and transfer, or “dump” it into another room.

Distributing the heat can help to lower the clearance requirements above the fireplace. With reduced clearances, some manufacturers will allow a TV to be mounted overhead.

Heat dump systems are typically available on higher-end fireplaces with higher heat outputs.

The firebox of a Direct Vent fireplace is sealed with a glass front and safety barrier screen. The sealed glass front allows for the Direct Vent system to work efficiently while preventing harmful byproducts from entering the home.

Tempered glass comes standard on most models while ceramic glass is offered as an upgrade. The safety barrier screen is in place to prevent direct contact with the heat of the glass.


Depending on the chimney you have and the gas fireplace you choose, you’ll either need co-axial venting or co-linear venting.

Co-axial venting is the most common and will consist of flexible or rigid, double-walled pipes that are installed in sections while co-linear venting requires two continuous flexible pipes. Co-linear venting is the least common of the two, as it's used for Direct Vent inserts only.

Direct Vent Fireplaces with co-axial venting systems have a flue outlet on either the top or rear of the firebox. This allows the venting configuration to be tailored to the installation.

Regardless of the flue outlet location, Direct Vent fireplaces with co-axial venting can be terminated vertically or horizontally, as long as the vent run meets the manufacturer's requirements.

Both vertical and horizontal venting can be maneuvered to avoid joists, beams, and wall supports.

Some manufacturers produce proprietary venting systems that must be used specifically with their gas fireplaces.

You’ll need to check the installation manual to see if the fireplace you’d like to purchase requires manufacturer-specific venting, or talk it over with an expert.


With so many venting options available, Direct Vent fireplaces can be installed in practically any location in your home, including the bedroom, basement, or even the bathroom.

Each city and state has specific code requirements, however, so you’ll need to check your local building and fire codes to make sure a Direct Vent fireplace can be installed in your room of choice.


Yes, when installed properly by a licensed professional, Direct Vent fireplaces are one of the safest options.

Since they use outside air for combustion and are completely sealed off from the interior of the home, you don’t have to worry about combustion byproducts polluting the indoor air.

As a precaution, you should still have carbon monoxide detectors installed in your home and have your fireplace serviced once a year by a licensed professional to clean and calibrate the burner.

It’s also very important that the fireplace is not operated without the safety barrier or glass front in place. If the glass front is removed, the fireplace will not work properly and combustion gases could enter the home.


Direct Vent fireplaces are available in linear, traditional, single-sided, multi-sided (peninsula), see-through, and corner styles.

Linear models are the most popular style today due to their sleek design and modern appeal.


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Ventless, or Vent-Free, gas fireplaces are free-standing units that don’t require a chimney or venting system of any kind.

Without a chimney for hot air to escape through, all of the heat produced by the burner is able to stay inside the home, making Ventless fireplaces extremely efficient and economical heating sources.

While the heat output is great, the overall look of the flame display is less intense than Direct Vent and B-Vent units. For this reason, Ventless fireplaces are primarily sold as heaters, rather than as decorative gas appliances.


Ventless gas fireplaces function on a closed-loop system of indoor air. Cool room air is pulled into the firebox to complete combustion. The air cycles around the firebox before flowing back out into the room as heat.

Ventless gas fireplaces are specifically engineered for nearly 100% efficiency, meaning little to no gases are left after combustion. What remains will typically be made up of water vapor and carbon dioxide. Any dangerous gases, like carbon monoxide, will be minimal and within safe limits.

As Ventless fireplaces burn oxygen, moisture is produced in the form of water vapor, which can leave condensation on your windows or throughout the room. This is especially true with liquid propane gas.

A small amount of moisture can be a great source of humidity during the dry winter months, however, a larger amount can cause mildew or mold growth.

If you notice excess moisture while using your Ventless fireplace, opening a window slightly will restore balance to the room. You can also install a hygrometer to keep track of the humidity levels and water vapor present in your home.

It’s generally recommended to use a Ventless fireplace for one hour at a time and four hours maximum in one day, to ensure oxygen and humidity levels remain normal.

Just like Direct Vent fireplaces, some Ventless fireplaces come with a safety barrier screen to provide protection from the fire. Safety barrier screens are not required by law for Ventless fireplaces, but they are becoming a popular addition for safety reasons.




Ventless fireplaces offer way more flexibility with installation since they don’t require a chimney, but they do have more restrictions when it comes to location, room size, media modification, and elevation.

Without a chimney or venting, air quality and oxygen depletion is a major concern. For this reason, Ventless fireplaces can’t be installed in small or compact rooms where the oxygen supply is limited.

If you choose gas logs for your media bed, they must be installed to the manufacturer's specifications and cannot be modified in any way.

Ventless gas logs are designed to fit together in a specific pattern to prevent flames from touching the logs. If flames touch the logs, flame impingement will occur and toxic gases will be produced. Without venting for the gases to escape through, these harmful byproducts will flow straight into your home.

Ventless gas fireplaces are also calibrated by the manufacturer to burn a specific air to gas ratio. This ensures little to no byproducts remain after combustion.

If you live in an area with a higher elevation, such as Colorado, you will most likely need to have the gas output on the fireplace adjusted to make up for the higher altitude and thinner air quality.

This adjustment can either be made by the manufacturer at the time of purchase or by a licensed gas professional during installation.

If you’re thinking about installing a Ventless fireplace in your home, you’ll need to research building, city, and state codes to find out if there are any installation restrictions and the minimum room size required.


Overall, Ventless fireplaces are considered safe, but they are relatively controversial due to the fact that if they aren’t functioning optimally, dangerous gases will be released into the home.

Some states, like California, have outlawed them for indoor use altogether, while others have strict installation requirements.

Vent-Free appliances are required to have a built-in oxygen depletion sensor (ODS) on the ignition pilot. The ODS monitors the oxygen level in the room and will shut off the gas supply to the burner if the oxygen supply dips below the safe threshold of 18%.

The BTU output of Ventless gas fireplaces is limited to a maximum of 40,000 BTUs per hour to ensure adequate oxygen is left in the room. For bathroom and bedroom installations, the maximum BTU output is even more limited, allowing only 6,000 to 10,000 BTUs, regardless of room size.

Since combustion air isn’t able to escape through a chimney, Ventless gas fireplaces will intensify any odors already present inside the home. The use of air fresheners, incense, and perfume, as well as the presence of dust and pet dander, will strongly affect the odor produced by a Ventless fireplace.

Exhaust from the fireplace can cause irritation to the lungs, as well. If you or someone in your household is sensitive to smells or has severe respiratory issues, like asthma or chronic bronchitis, you should not install a Ventless gas fireplace.


Ventless gas fireplaces are available in the same styles as Direct Vent fireplaces with linear being the most popular choice.


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B-Vent fireplaces, also known as Natural Vent, are the least popular gas fireplace option today.

They are more affordable than both Direct Vent and Ventless fireplaces, however, they are extremely inefficient and have less flexibility when it comes to installation.


B-Vent fireplaces feature an open-front design and operate similarly to wood burning fireplaces. They pull fresh air into the firebox from inside the home for combustion and use a vertical pipe to carry away exhaust and fumes.

Most of the heat produced by the fire will also escape through the venting, making B-Vent fireplaces very inefficient. For this reason, B-Vent fireplaces are most often used for aesthetic purposes rather than as a supplemental source of heat.


B-Vent fireplaces use a double-walled, insulated pipe to encourage the natural movement of air needed to exhaust combustion gases.

The airspace between the inner and outer pipe provides insulation, preventing heat loss and allowing the inner pipe to warm up quickly so warm flue gases can rise up and out of the top of the pipe with ease.

B-Vent pipe is the most affordable type of venting and is relatively easy to install. The major drawback is that it must be installed vertically through the home and terminate above the roof.


B-Vent fireplaces are slightly more limited when it comes to installation than Direct Vent or Ventless gas fireplaces.

Similar to a masonry chimney, the venting for B-Vent fireplaces must terminate vertically through the roof of a house. This limits the location of installation to areas where a vertical pipe can run straight up to the roof.


Yes, B-Vent fireplaces are safe. With vertical venting to exhaust combustion byproducts, you don’t have to worry about dangerous gases building up in your home.

Some B-Vent fireplaces feature a sensor that will shut off the fireplace if a downdraft occurs and forces exhaust back down the chimney into the home.


B-Vent fireplaces are available as inserts and customizable masonry fireboxes.

Customizable fireboxes allow you to design the finish to match your home’s décor and give you the ability to choose between a contemporary or traditional look.



There are two main ignition systems for gas fireplaces - intermittent pilot ignition (IPI) and continuous pilot ignition (CPI). For both ignition systems, the pilot is lit initially using a switch on the fireplace.

Once the flame is established, a flame-sensing thermocouple will register the heat and send an electrical current to the gas valve. The gas valve opens, sending a constant stream of fuel to the pilot light. If the flame ever goes out, the thermocouple will cool down, stopping the electrical current, and shutting off the gas supply.

With an IPI, the pilot will stay lit as long as the fireplace is on. Once the fireplace is turned off, the pilot will go out. IPI’s are best for warm weather climates, or areas where you won’t be using your fireplace every day. They will save you gas, however, the initial start-up will take between 15-20 seconds each time you turn the fireplace on.

With a CPI, the pilot is continuous, meaning it will always stay lit unless there is an issue with the gas supply. CPI’s are best for cold-weather climates, or areas with long winters where you’ll be using your fireplace often. The presence of the flame keeps the firebox and flue warmer than freezing and the pressure difference in the firebox low, allowing for a smoother start-up process.

Most gas fireplaces feature a battery backup in case of a power outage. With battery backup, you’ll be able to turn the fireplace on during a power outage, but any features that require electricity, like lights and blowers, will not work.


Most gas fireplaces come with a hand-held remote control or a wall switch.

Basic remotes will turn the fireplace on and off whereas full feature remotes can control the ignition, blower, lighting, heat output, flame height, thermostat, and timer.

Some gas fireplaces can even be integrated into your Smart Home system, allowing you to control the fire using a wall-mounted touch screen control panel or via an app on your smartphone.


Most gas fireplace manufacturers give you the option to choose the surround (trim) and media bed.

Surrounds come in various widths, colors, textures, and materials, making it easy to match your home’s décor.


Gas logs are the most popular choice for an authentic burning display while fire glass, river rocks, and fireballs are contemporary options.

Gas logs offer the same look and feel of a traditional wood burning fireplace with the added convenience of gas. Most gas fireplaces come with an approved gas log set that’s specifically designed to fit the firebox.

Fire glass comes in an array of colors and is available in round/oval gems or crushed glass.

Monochromatic river rocks or fireballs will create a uniform burning display, but you can always mix and match colors and sizes to create depth and visual interest.

For a non-traditional look, pairing artistic media, such as Napoleon’s Nickel Stixs, with fire glass will create an ultramodern focal point.


A fireplace blower is a type of fan that helps to blow more heat from the fireplace out into the room.

Blowers don’t make gas fireplaces more efficient, but they do help to increase the overall heat output. Similar to a fan, blowers are not silent and will make a whirring noise while in use.

Power Vent

Power venting is primarily used in commercial settings, such as condominiums, high-rise buildings, and tall apartment complexes where traditional venting won’t work.

A fan is installed in-line with the venting system either where the venting system begins (close to the fireplace) or where it ends (close to the roof or wall). The fan pushes/pulls the exhaust through the venting and up and out of the building.

This allows for installation through areas where venting has to run down, across, and then up to the roof, rather than straight up, such as through a crawl space.

Power venting solutions are specific to the manufacturer.


Cleaners are available to keep your gas fireplace looking like new. You can use a glass and hearth cleaner periodically to remove any build-up from the inside of the ceramic glass front.

To remove sooty residue from your gas logs or burning media, simply using plain water and a soft cloth will do the trick. Harsh cleaning agents can cause gas logs to become brittle over time making them more susceptible to breakage.


Need some help choosing the best gas fireplace for your space? We're here for you! Call our NFI certified experts at 800-919-1904 today.


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