Installing Ventless Gas Logs In Existing Fireplace

While wood-burning fireplaces are the dream of most homeowners, most of today’s new fireplaces are fueled by gas. Gas comes with multiple advantages, including greater availability and reduced maintenance. You never have to worry about messy ashes and soot left over by burning wood.

However, gas fireplaces come with one major challenge – the risk of oxygen depletion. In traditional gas fireplaces, similar to conventional wood fireplaces, an exhaust vent (flue) is incorporated into the fireplace to remove harmful fumes from the home.

Many homeowners use the existing chimney to run the flue. It’s a simple process. But here’s the question – what happens if you don’t have a chimney?

This is where a ventless gas fireplace comes in handy. These fireplaces don’t need a chimney because they don’t need to vent the exhaust gases.

So, what about carbon monoxide and sulfur dioxide, one would ask? Wouldn’t that create a considerable risk to the home’s occupants? We find out shortly.

What is a Ventless Gas Log?

There are two broad categories of gas fireplaces – the traditional vented gas fireplace and vented gas logs.

The traditional vented gas fireplace can be fueled by either propane or natural gas. More importantly, it’s characterized by two vents running to the exterior of the house.

The first vent draws fresh air (rich in oxygen) from outside the house to aid the combustion. Meanwhile, the second is an exhaust vent that safely removes exhaust gases generated inside the fireplace.

Ventless gas fireplaces are slightly different. Although they also run on either natural gas or propane (some are even dual-fuel, capable of running on propane or natural gas with a few modifications), the two flues/vents mentioned above are missing. There’s neither an air intake vent nor an exhaust flue.

Ventless gas logs are a subcategory of vent-free gas fireplaces. Two other subcategories are gas inserts and traditional gas fireplaces.

The only thing you need to remember is that gas logs are hollow perforated imitation (often ceramic) logs used as a burner in the fireplace. The gas log sits inside the fireplace to create a wood fire experience.

The log itself doesn’t burn. It’s only there for aesthetics.

How Does a Ventless Gas Log Work?

Gas logs mainly comprise the set of ceramic logs and piping. The logs can be placed in many different setups depending on the desired ambiance. The pipes pump gas fuel through holes in the logs. The log is installed inside an existing fireplace.

When the log set is ignited, a flame is produced that dances over the ceramic log set, creating a near-life-like wood burning experience. The ignition can be done via a manual knob or remotely. It depends on the gas log model.

The installation technician usually fireproofs the entire fireplace to ensure complete safety during operation. For instance, you may need to line the fireplace’s interior with lava rock and sand to ensure that the fire doesn’t spread out. A glass panel is also typically installed to contain the fire.

Since the ventless gas heater has no exhaust vent, gases generated during the combustion process are released into the house. Also, since there’s no inlet vent, it draws air from the home to enable combustion.

What’s the Upside?

Why do they even make ventless gas logs in the first place if they’re so dangerous? Why not just do away with them altogether?

The short answer is – efficiency. Vent-free gas fireplaces are one of the most efficient forms of gas heating; some models are virtually 100% efficient.

For context, the standard furnace is about 80% efficient, with some of the most efficient models rated 80% AFUE (Annual Fuel Utilization Efficiency).

This means that 80% of the fuel goes toward generating useful heat, while the other 20% is lost. Condensing furnaces are slightly better at around 92%. Many ventless gas heaters are 99.99% efficient. Less than 0.1% of the fuel is wasted.

This extremely efficient burning process typically generates only two by-products – water and carbon dioxide – both of which are harmless. Indeed, even the CO2 is produced in minor traces.

Pros and Cons of Ventless Gas Logs

Ventless Gas Log Pros

Though a controversial product among consumers, the ventless gas log (and vent-free gas fireplaces in general) are known for several advantages;

  • Incredible heating efficiency: This is, by far, the biggest advantage of vent-free gas logs. They are incredibly energy efficient. Whereas the vented gas log carries nearly 20% of the combustion heat outside via the flues, the ventless model retains all the heat inside your house. The result is better heat levels and reduced heating bills.
  • No inbound draft: Although useful, the inlet flue in vented gas fireplaces creates a pathway for cold air to enter the home. This negates the purpose of heating the home in the first place. Why bother heating when you’re creating a path for cold air to enter the home? Vent-free fireplaces remove this inefficiency.
  • Easier to install: Compared to vented gas logs, unvented models are a lot easier to install. For one, you don’t need to purchase flues. Secondly, you don’t need to remodel to create a path for the flues. The greater ease of installation often translates into reduced installation/upfront costs.
  • Retain/add moisture indoors: The vented heater gas log carries all moisture outside the house. This may leave indoor air a tad dry, creating new health problems. Vent-free models retain indoor moisture and continually add combustion moisture to the house for greater humidity.
  • Affordable: Finally, ventless gas logs are the most affordable type of gas fireplaces. Considering that they are also cheaper to install, they make a worthy choice when shopping on a budget. Remember that you still need professional installation. Never attempt to DIY-install a vent-free gas fireplace.

Ventless Gas Log Cons

Despite the many advantages, however, ventless gas logs come with a few strong downsides that you must keep in mind;

  • Oxygen depletion risk: This is a major concern for ventless gas fireplace users. Since the fireplace draws from the house all the oxygen it needs for the combustion process, there’s a significant risk of oxygen depletion. Where there’s oxygen depletion, there’s likely to be carbon monoxide – a fatal gas.
  • Your state laws may not permit it: Owing to the high risk it poses, ventless gas fireplace heating is tightly controlled throughout the country and right out banned in some states and municipalities. In California, for instance, the use of unvented fireplaces is completely prohibited. So, check your local codes before you head out shopping.

How to Install Ventless Gas Logs in an Existing Fireplace

As earlier mentioned, installing the ventless gas log fireplace is a job for the pros. You must never attempt to install a vent-free gas log on your own. The risks are too much.

Nevertheless, it’s always nice to know how the installation process works. The following is how ventless gas logs are installed in an existing fireplace.

Questions to Consider

  • Are you sure you prefer ventless logs over vented logs?
  • Is the fireplace going to need natural or propane gas?
  • Manual or remote control – which is your preference?
  • What type of fireplace do you have? Masonry or pre-fab?
  • What do your building and city codes say about ventless gas logs?

Preparing for the Installation

After you’ve answered the above questions, there are a few things to get in order before the actual installation begins;

  1. Install a carbon monoxide detector in your home: The carbon monoxide detector helps track the presence and levels of unburned fuel and rings an alarm if dangerously high CO levels are detected. Remember that CO cannot be detected by scent or sight.
  2. Clean up the fireplace and get rid of extra debris: Remove the old gas logs. Consider spraying the smoke chamber with a bottle of insulated mortar. Also, you can coat the interior of the fireplace with high-temperature paint. Allow the area to dry fully before moving to the next step.
  3. Take out the masonry screws: You also want to remove the grate that was installed into the firebox.
  4. Shut off the gas line: You can disconnect the gas supply from the burner. You can connect the gas line to your new burner after the firebox is thoroughly cleaned and cleared. Apply thread sealer around the gas line before connecting it to the burner.

The Actual Installation

  1. Place the burner in your preferred position to see where you need to drill the holes for your masonry screws. Once the holes are drilled, screw the burner into place.
  2. Install the grate over the burners. Be sure that the two are properly installed and tightened as appropriate.
  3. Inspect the set up for leaks by spraying a simple water and soap mixture along the gas lines. If you notice bubbles, there’s a leak. Tighten the connection or replace faulty pieces as necessary.
  4. Place the gas logs on top of the grate. Remember not to handle the logs with bare hands. Use garden gloves to protect your hands.
  5. Add fine granules (if you’ve acquired some) underneath the logs and over the burner. Granules help disperse the flame for a more life-like appearance.
  6. If the gas log came with accessories, add them around the logs. Alternatively, you can find and add your own accessories for a realistic touch.
  7. Your gas log fireplace is ready! Turn it on and enjoy the warm glow of the flame and embers.

Ventless Gas Fireplace Safety

We’ve mentioned repeatedly that ventless gas logs aren’t very safe in the home. If you decide to acquire one anyway, the following several safety tips to consider;

Gas logs aren’t meant for gas fireplaces

It sounds counterintuitive, but it’s the truth. Gas logs are designed to help homeowners convert the traditional wood-burning fireplace into a gas-burning fireplace. A manufactured gas fireplace can’t handle the amount of heat or exhaust produced by after-market gas logs. It may cause the fireplace to crack or melt, creating a fire hazard.

Ensure your carbon monoxide detectors are working

It is one thing installing carbon monoxide detectors and another having them working. So, install the CO detectors in the room where the ventless gas log will be used and, more importantly, make sure to test them twice a year. The best time to inspect them is when daylight saving time changes.

Ensure children can’t reach open flames

Although gas logs aren’t real wood, the flame in a gas fireplace produces real flames. The logs won’t send sparks into your room, but occasionally, you may see ceramic chips due to the rapid expansion inside the fireplace. These chips can become projectiles. Consider a fireplace screen or glass door with a mesh behind the glass for extra protection.

Don’t burn the gas log with the glass door closed

Doing so causes the burner to produce excessive amounts of soot and carbon dioxide. Furthermore, the heat build-up inside the unit can melt components and creates the risk of an explosion.

If it’s not safe for wood, it’s not safe for gas

If your HVAC inspector or chimney sweep has declared the wood fireplace unsafe for wood, don’t use it for gas fire either. Usually, the inspector or chimney sweep will say the chimney isn’t properly insulated or has leaks. Heating in a leaky or improperly insulated fireplace creates a huge risk of asphyxiation and fire, respectively.

Always replenish indoor oxygen 

Ventless gas logs deplete oxygen in the home, creating the risk of CO poisoning. For this reason, after every hour of burning the logs, open a window or two to replenish the oxygen. Also, it’s strongly advised that you never burn a ventless gas log for four continuous hours. After, say, four hours, turn it off to replenish the oxygen.

How to Clean a Ventless Gas Log

Regular cleaning is mandatory when using ventless gas logs. It keeps the logs working effectively and burning efficiently with minimal waste. Proceed as follows;

  1. Get a vacuum cleaner with a hose and preferably a brush on the end of the hose.
  2. Using the vacuum, remove surface dust from the bottom of the fireplace around the gas log burner. Then, remove the log set from the burner and vacuum it too.
  3. Locate the pilot light and remove dust from the air intake going into the main burner. This is the part that draws oxygen from the room. If this part is clogged, there’s incomplete burning. Use compressed air to blow the air intake.
  4. Locate the oxygen depletion sensor (it’s located right below the pilot light) and again used the compressed air to flush any debris trapped inside.

You’re always encouraged to consider professional cleaning as the pilot light and oxygen depletion sensor must be handled with care.

Ventless Gas Log FAQs

  • Can a ventless gas log fireplace be vented? No. Unfortunately, there’s no way to convert a ventless fireplace into a vented one. Your only alternative is to tear down the ventless model and replace it with a vented unit.
  • How do I stop my ventless gas logs from smelling? Improve the air quality in your home. Also, if you smoke, consider doing it outside. Additionally, vacuum the house regularly and avoid the use of harsh cleaning chemicals and plug-in deodorizers.
  • Do gas logs need to be replaced? Yes, you need to replace your gas logs. Ideally, the logs should be replaced every 2-3 years, though newer ceramic gas logs can last much longer.

Best Ventless Gas Logs

1. Peterson Real Fyre 18-Inch Charred Oak Stack Gas Logs

Fireplaces are all about the elegance first and then the heat. Peterson’s Real Fyre gas logs are handcrafted, hand-painted, and guaranteed to grace your home with unmatched individuality, exceptional aesthetics, and unbeatable quality.

This particular log set from the Charred Oak series is as close to real-life wood-burning as you can get. Each log is carefully shaded and detailed with textured bark and knotholes to create a life-like smoldering fireplace experience.

You’ll love that the log set comes with a custom log grate included. Glowing embers, silica sand, a damper clamp, and a bendable connector kit also come standard.

You’ll also find the installation instructions inside. The unit is constructed with ceramic and reinforced with steel rods for added durability


  • Up to 35,000 BTU
  • Realistic logs and flame presentation
  • Flexible installation options
  • Lifetime warranty


  • Burner selected and purchased separately
  • Pricey at close to $300

2. HearthSense Model #VF24LA-2 Ambi-2 Liquid Propane Gas Log Set

If you’re willing to spend even more, you should take a look at the model #VF24LA-2 Ambi-2 gas log set from Hearth Sense. Rated at 34,000 BTU, this fireplace is more than sufficient as a supplementary heater in spaces up to 1,400 square feet. It’s also very stylish and guaranteed to add a touch of style to your home.

In total, the set comprises seven (7) handcrafted and hand-painted realistic-looking concrete logs and comes with a 6-LED ambient light system. The LED light system is installed at the back of the log set and, when switched on, creates a warm glowing effect in the firebox.

The log set is 99.9% efficient and doesn’t need any external ducts or chimneys. A manual on/off millivolt control is included to make temperature control easy, while several safety features, including an oxygen depletion sensor, protect home occupants from any dangers.


  • Ideal for up to 1,400 square feet
  • Push piezoelectric ignition
  • Built-in pilot
  • Millivolt control included
  • 1-year warranty


  • Priced at close to $400
  • Manual controls

3. Duluth Forge model 210065 Ventless Propane Gas Log Set

Duluth Forge ventless gas logs offer a charming alternative to traditional heating in the home in that they allow you to enjoy the warmth and feel the ambiance of the fireplace without the fire. The log sets can be placed anywhere in the house and deliver up to 33,000 BTU for toasty evenings, even in freezing-cold winters.

The log set comprises eight (8) hand-painted realistic ceramic fiber logs set atop an ember burner chassis designed to provide one row of flames and a glowing ember bed to create a realistic fire. Other key highlights of the log set include battery-assisted piezoelectric ignition and customized heat settings.

The unit is 99.9% efficient but still comes with an oxygen depletion sensor for safety. It also features an automatic shutoff for increased safety. A one-year warranty backs the log set.


  • Powerful 33,000 BTU heater
  • Ideal for up to 1,300 square feet
  • Stylish, hand-painted logs
  • Burner chassis and bag of embers included
  • 1-year warranty


  • Manual controls
  • No thermostat

4. ProCom Heating PCS150T Ventless Fireplace Insert

Finally, this ProCom model PCS150T is a zero-clearance gas log with an elegant style and four (4) ceramic fiber, hand-painted logs to add heat and timeless ambiance to your home, den, or kitchen.

It’s powered by Procom’s dual-fuel technology, allowing it to use either propane or natural gas. You can expect up to 15,000 BTU of gentle heat when the unit is running at maximum capacity.

You’ll quickly note that this is the only product on this list that features an in-built thermostat. The variable-control thermostat offers customizable temperature settings, allowing you to adjust indoor heat levels to suit your precise needs.

The log set is 99.9% efficient, with a dual-precision ported vent-free gas burner, and doesn’t need any external ducts or chimney. It operates on piezoelectric ignition and has a built-in oxygen depletion sensor for auto-shutoff.


  • Patented dual-fuel technology
  • Stylish, hand-painted gas logs
  • Piezoelectric ignition
  • Oxygen depletion sensor in-built
  • Ideal for up to 800 square feet


  • Low heat output at 15,000 BTU

Wrap Up

Ventless gas logs aren’t a very popular choice for home heating because of the associated safety risks, especially carbon monoxide (CO) poisoning. However, it’s a worthy alternative to vented gas fireplaces in some regions as long as you observe safe use practices.

For instance, vent-free gas models are inexpensive and produce a lot more heat than vented gas fireplaces. Their efficiency is also unmatched. Just make sure to use it safely.