Gas Log Buyer's Guide

Can’t decide between vented or ventless? Here are the pros and cons of both vented and ventless gas logs all in one convenient place for you.

The different styles of gas fireplace logs available are vented gas logs and ventless gas logs. There are pros and cons to both models but the main difference is vented gas logs require a chimney or flue and an open damper to be safely operated. Ventless, or vent-free, gas logs can be installed without the need for a chimney allowing for more customization into where you want your gas log installation.

Vented Gas Logs

Vented gas logs produce a byproduct of carbon monoxide that needs to be allowed to escape to the outside through a chimney or flue. Every time these appliances are used, the damper must be opened, just as with a wood-burning fireplace.

The good news is these gas logs are much more realistic-looking than ventless gas logs. The flames are much taller and will flicker around much like a wood-burning fire. It is for this reason that vented gas logs are a good choice for people thinking of making the switch from a wood-burning fireplace to a gas fireplace.

Pros of Vented Gas Logs

More efficient than a wood-burning fireplace
More realistic looking than ventless gas logs
Taller flames
Logs can be customized and rearranged for a pleasing display
No BTU limit
Flames can touch logs

Cons of Vented Gas Logs

Less efficient
Costs more
Emit more pollution
The damper must stay open
Heat loss through the chimney

Shop Our Most Popular Vented Gas Log Sets

Ventless Gas Logs

Ventless gas logs (or vent-free gas logs). don’t need a chimney. Don’t be mistaken, these gas logs can still be installed in a house or fireplace with a chimney. The damper can remain closed while the fire is burning.

Because of the lack of chimney needed for the functioning of these gas logs, the heat will not escape outside through the chimney or flue, and will instead stay inside your home. Therefore ventless gas logs will heat up a room much quicker and effectively than the vented gas logs. Another side effect of this phenomenon is less fuel is needed to fuel the flame creating a more efficient system.

And finally, ventless gas logs will emit a significantly less amount of pollution, in the form of carbon monoxide that is released into the atmosphere through the chimney.

Ventless gas logs are less realistic-looking than their vented counterparts. The flames are smaller and more stagnant because they lack the airflow from an open damper, and often will burn in a pre-programmed pattern.

Ventless gas logs also come with oxygen depletion sensors. Because this design uses air from the room for combustion, there will be an attached oxygen depletion sensor to shut off the logs if the oxygen gets to a low level. It is not recommended to let ventless gas logs stay on continuously for extended periods of time. The other byproduct of ventless gas logs is water vapor.

This will create a bit of humidity in the room the fireplace is located in and can be counteracted by cracking open a window. Finally, this design will not allow any odors produced by the gas-burning to escape through the chimney and will release a smell the longer it burns, this is why ventless gas logs are not recommended for people with asthma or allergies.

Pros of Ventless Gas Logs

Heats your home faster and more efficiently
Less expensive
Chimney not required, leading to easier installation
Less pollution emitted
Less gas consumed
Comes with an oxygen sensor

Cons of Ventless Gas Logs

Not as realistic display
Not recommended to run for extended periods of time.
Adds humidity into the home
Not legal in some states such as California and Massachusetts
6,000-40,000 BTU limit
Produces odors that cannot escape through the chimney
Not recommended for people with allergies

Shop Our Most Popular Ventless Gas Log Sets

What are Gas Logs Made of?

Gas logs are made from either ceramic fiber or a refractory cement mixture—materials that can handle high temperatures for extended periods of time. Sometimes steel bars are added to the inside for reinforcement, to prevent cracking after being heated many times over.

Newer models of gas logs have each log individually molded from a cast of real tree branch samples, and carved to match the unique details found in natural tree wood. This is to create to most realistic logs possible. Vented gas logs typically have orange and yellow flames. Ventless gas logs, with their smaller flames, usually have a blue-ish tint.

Components of a Gas Log Set:

Gas valve: Controls the release of gas to fuel the flame.

Pilot assembly: Where a small flame is kept lit and will light the fire. This is often where the oxygen depletion senor in ventless gas logs is located.

Burner: Where the flame is produced.

Steel Grate: Holds the logs in place and creates a raised platform for the burner, gas supply line to rest under.

Logs: the ceramic tree branches the flame appears around.

Sand or Vermiculite: Facilitates the distribution of gas in the burner pan of vented gas logs.

Glowing Embers: Give the flame a more realistic appearance.

Damper clamp: keeps the chimney’s damper from closing, making sure no dangerous gases leak out of the firebox.

Getting the Correct Size Logs for your Fireplace

Gas logs come in a range of different sizes and arrangements. It is important to get the correct size for your firebox because getting a set that is too large will overheat your firebox and gas valves and cause permanent damage to your logs, your fireplace, or your home.

Steps to Measure Your Fireplace:

Measure the front width of your firebox.
Measure the rear width.
Measure depth and height.
Use these measurements to select the right gas logs for your fireplace.

Gas Log Control Options

Match-Lit

Match-lit ignitions are simple, budget-friendly, and require manual lighting. The system doesn't include a pilot or valve assembly. You'll simply place a match or lighter near the burner and turn on your gas supply with the included gas key valve.

Match-lit systems are only available with Vented gas log sets fueled by Natural Gas.

Manual Safety Pilot

Manual Safety Pilots, or Safety Pilot Kits (SPKs) have flame-sensing thermocouples. Instead of lighting your log set with a match, you'll turn on your gas supply, push a knob on the gas valve, and turn it to the "On" position.

Once your log set ignites, you can release the knob and the pilot stays lit. If the flame goes out, the system automatically shuts off your gas supply.

Modified Safety Pilot

Modified safety pilot systems are just like SPKs with motors connected to the gas valve. You'll be able to connect a remote control or variable control to your log set for user-friendly operation.

Millivolt Valve

Millivolt gas valves are also similar to SKUs. They use a thermopile to generate a larger millivolt current. This allows you to connect a remote control, wall switch, timer, or thermostat to your gas log set.

Millivolt systems don't require external power, because they operate solely off the pilot light, which stays lit.

Electronic Valve

Electronic ignition systems are the safest and most convenient way to operate your log set. Some require a source of power, but most are battery-operated. With an electronic gas valve, the pilot will not stay lit.

You can turn the pilot light on and off and adjust the flame height on your gas log set using a remote control, a wall switch, or a switch on the gas valve.

FAQ's

Can I use propane gas or natural gas for my fireplace logs?

Many gas log sets are compatible with both propane gas and natural gas. Be sure to select a set that matches your home's gas line type. Some logs are designed specifically for one fuel type, so it’s important to check the manufacturer’s specifications before purchase.

Are gas log sets safe for existing fireplaces?

Yes! Gas log sets are designed for existing fireplaces, whether vented or ventless. For vented sets, the chimney damper must remain open, while ventless logs require proper placement and adherence to the recommended log stacking pattern to maintain safety and proper flame appearance.

How realistic do gas logs look compared to natural wood?

High-quality fireplace logs — especially refractory ceramic logs — can mimic the look and texture of natural wood, complete with lifelike bark and ember details. Vented logs tend to have taller, more dramatic flames, while ventless logs prioritize functionality and heat efficiency.

Can I adjust or move the logs in my gas log set?

It depends on the type of gas log set. Vented logs can often be rearranged to achieve a customized look, while ventless sets must follow a strict placement pattern to prevent direct contact with flames, ensuring proper functionality and safe operation.

We're Here to Help!

We are here to help! Fireplace Deals’ inventory has dozens of design options for your perfect installation—whether you’re focused on a more efficient burn or having the most inviting centerpiece for your next family get-together. Changing up your home’s fireplace can be a daunting task, but our Learning Center has dozens of articles to educate you on the process, and if you have any more questions, send an email or call 866-848-3473 to speak with an NFI-certified expert.

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Vented vs Ventless Gas Logs

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