Can You Use Vent Free Gas Logs In A Vented Fireplace?

You can use vent-free gas logs in a vented fireplace since the vent-free gas logs are already designed to showcase a fireplace in a room that doesn’t have a flue or chimney. One advantage to using those logs, instead of the vented type, is that you won’t have to open the damper since no venting is required.

You’re probably burning (pun intended) with other questions about vent-free (also called ventless) versus the vented fireplaces, so let’s dive in. I’ll tell you more about how to distinguish between those gas logs (and fireplaces), the potential of interchanging them back and forth, and the benefits and drawbacks of both versions. 

How to Tell if Gas Logs are Ventless

In contrast to a vented fireplace, the ventless version will have a cylinder attached to the gas line that connects to the burner underneath the logs. You can look for this small cylinder near the hole in the floor or wall where the gas line emerges. 

This cylinder is called an “oxygen depletion sensor” and is required for a ventless fireplace because there is no vent to remove the exhaust fumes. 

Another way to tell is to look at the logs as the propane burns, and the flames emerge. If the logs are vented, you will see tall yellow flames—which many people enjoy watching. In contrast, the flames that dance around ventless logs are more restrained and appear blue. 

Can a Vent Free Gas Fireplace be Vented?

Unfortunately, you cannot vent a vent-free gas fireplace because it would have been designed vent-free and not use any products that emit exhaust fumes resulting from burning the propane supply. 

If you wish to convert to a vented gas fireplace, you should hire a professional to replace the entire set and install a vent. 

Differences Between Vented and Unvented Gas Logs

Simply put, vented gas logs produce a more realistic and pleasing flame and are less efficient in heating the room since much of the heat escapes along with the exhaust through the flue. 

In contrast, ventless gas logs typically produce a low blue flame and channel far more heat into the house. If you are still nostalgic for a wood-burning fireplace, a vented set might reward you with the ideal transition that you seek.

Differences Between Vented and Unvented Fireplaces

One key difference is that a traditional vented fireplace has two vents that channel airflow between the outside and the inside of the house. One vent brings in a fresh outside air supply to help the fire combust more efficiently. The other vent safely disperses the exhaust gases. 

In contrast, the ventless fireplace would have no connection to the outside, which makes it appealing in the simplicity of installation and versatility. In addition, ventless fireplaces are engineered to burn propane so efficiently that they pass rigorous air quality testing in laboratories. 

One budgetary consideration is that vented fireplaces are generally more expensive than ventless due to the requirement to install those two vents at the back of the fireplace. 

Vented Gas Logs—Pros and Cons

Now that we’ve skimmed the basics, let’s take a look at the pros and cons of vented gas logs:


  • Fire looks more realistic and pleasing.
  • Exhaust fumes are channeled outside, thus reducing the risk of contamination. This also reduces the odor of combustion inside the room.


  • Heat efficiency is reduced since much of the heat is carried through the flue.
  • The gas line won’t have an oxygen depletion sensor. However, since much of the exhaust is removed outside, the danger may be minimal.
  • This version typically consumes more propane than a ventless fireplace.

Ventless Gas Logs—Pros and Cons


  • Heat conduction is incredible; your room will be toasty warm.
  • You would undertake much less renovation to set up since no vent is required to link to outdoor air. Hence, this type of fireplace can be more versatile as to placement within the house.
  • Built-in safety feature: the oxygen depletion sensor will warn of carbon monoxide danger, for example, and shut down the flow if necessary. 
  • Those ventless fireplaces have been tested to operate within the range of safety in circulating combusted gases back into the home’s interior.


  • Some customers may feel less enthusiastic as to the look and feel of the fire generated by the propane.
  • Some states and provinces may have laws prohibiting a ventless fireplace inside your house; check with your local contractor. 
  • Since there is no vent, some frequent airing of the room through an outside window may be necessary to restore plentiful oxygen.
  • Burning propane cleanly may introduce water vapor and carbon dioxide, so be careful of excessive moisture in the room.

Installing Ventless Gas Logs in an Existing Fireplace

Suppose you have a wood fireplace, along with a charming chimney. You’re tired of finding firewood; maybe you’ve even had enough of chopping it. You’ve heard so much about the benefits and efficiency of gas fireplaces. Should you convert? 

Certainly, yes! The critical thing required is to have a professional install the gas line required to supply propane to this new gas fireplace. 

A professional will know the local building code and city by-laws. They will inspect the chimney to see if it’s ready for use, and if necessary, clean it. Also, once you have it installed, a licensed professional should inspect the gas insert once a year.

Do’s and Don’ts for Ventless Gas Logs


  • Monitor carefully the humidity in the room from time to time since the ventless gas logs could release excess moisture if operated for long periods.
  • Make sure any new gas logs you buy aren’t of the vented kind since they release residue that should be properly vented.


  • Don’t order a ventless fireplace if someone living at your house has respiratory issues, such as asthma or chronic obstructive pulmonary disease. Although the propane burns cleanly, there are still low nitrogen dioxide concentrations, which is a minor irritant. 
  • Don’t leave combustible materials too close to the ventless fireplace. Since it operates at an intense heat capacity, it could cause combustion if care isn’t taken.

You may find a handy, neutral guide to maintaining ventless fireplaces (as applied to the United States of America) here on this non-profit website:

Dealing with Moisture Issues

As discussed, one issue is the generation of moisture. See this chemical equation below:

C3H8 + 5O2 → 3CO2 + 4H2O

In this equation, C3H8 is propane in chemical form, and O2 is oxygen. When propane burns, it combines with oxygen and generates carbon dioxide, CO2, and water, which you know to be H2O. 

This is why it is recommended that you do not leave on a ventless gas fireplace for long periods, and not when you are out of the house. A ventless gas fireplace is not intended to be the primary source of heat for the house.

As long as you use ventless gas logs only long enough to enjoy viewing the fire and enhance the room’s décor as you are resting, the moisture in the room will naturally dry up over time. In addition, if people enter and leave the room several times a day, or you effectively use the house’s ventilation system, these habits also help reduce moisture. Alternatively, you may use a dehumidifier the occasional time. 

“Curing” the Gas Logs Upon Purchase

When installing a brand new ventless fireplace, it’s important to “cure” the logs, which means burning off the residue left behind by the manufacturing process. This means running the unit (leave the room’s windows open during this time) at its hottest temperature for about five hours and be sure to remain in the house to check on the progress. 

This “curing” needs only be done once and should be undertaken before you start using the fireplace regularly.

Cleaning the Ventless Fireplace Windows

Over time, minerals from the ventless gas logs, like soot, may coat the fireplace glass. To clean the glass, ensure that the fireplace has not been on recently. If it has, let it cool so that it is back to room temperature. You may do this cleaning twice a year. 

When selecting a cleaning product, avoid those that have ammonia. If any ammonia film is left on the glass, starting the fireplace again after could permanently etch the glass, so it is best to avoid using ammonia. Examples of products that have ammonia are window cleaners, oven cleaners, and multi-surface cleaners. 

Use a soft cloth, like a rag or microfiber cloth, to clean the glass. Do not use paper towels as they are chemically treated for absorbency, which is their primary function. Consequently, paper towels can leave a film on the glass, which could be “baked in” when you re-start the fire. You could also buy “glass towels” that are available among paper towel products. 

Finally, do not use abrasive cleaning solutions, such as scouring powders or pads. Those are harsh upon glass and could etch the surface.