It is the question we hear most in the gas log aisle, and the answer is usually decided by the fireplace, not by taste. Here is how to work it out before you come in.
Call them gas logs, cement logs, or ceramic logs, the logs themselves are the easy part. They are cast from refractory cement or ceramic fiber, painted by hand, and they sit on top of the part that matters: the burner. The burner is either vented or vent-free, the two are not interchangeable, and which one your fireplace can take is usually settled before you pick a log style.
Vented logs burn like a wood fire. Tall, lazy yellow flames, a heavy ember bed, and the damper open the whole time, which means most of the heat goes up the chimney with the exhaust. You are buying the look, and they are very good at the look.
Vent-free logs burn with the damper closed. The flame is smaller and tighter, and because nothing goes up the flue, nearly all the heat stays in the room. They are sized to the room, they carry an oxygen sensor, and they are the kind the gas code has the most to say about.
Our gas logs page has the two side by side in a table. What it cannot do is look at your fireplace. So, in the order we would check it:
A vented set needs a fireplace that could safely burn wood right now: a masonry firebox and flue in good repair, or a factory-built wood-burning fireplace whose paperwork allows a gas log set. The damper has to stay open while the set runs, and every vented set we install gets a clamp so the damper cannot be closed by accident. If the chimney has not been looked at in a few years, or you can see daylight through a crack, vented is off the table until it is inspected and cleaned. The exhaust from a vented log set has to go somewhere, and the somewhere has to be sound.
A vent-free set needs none of that. No working chimney, no open damper. It can go in a fireplace whose damper closes, or in a ventless firebox built for it. The one place it cannot simply be dropped in is a factory-built fireplace, the prefab metal kind, unless that fireplace has been tested and listed for an unvented appliance. Plenty have not, and the label inside the firebox door is where the answer lives.
The quick tell: if your chimney is sound and the damper works, you can choose. If the chimney is bad, blocked, or not there, vent-free is your option. If the fireplace is a prefab unit, check its listing before assuming anything.
Georgia's state minimum gas code is the 2024 International Fuel Gas Code with Georgia amendments, in force since January 1, 2026, and it treats a vent-free log set as an unvented room heater. Four rules from it come up on nearly every job:
Where a set can go matters too. The code keeps unvented appliances out of bedrooms and bathrooms, with a narrow exception for small wall-mounted heaters, 10,000 BTU in a bedroom and 6,000 in a bathroom. A log set is not that, so a bedroom fireplace is a vented-logs fireplace, provided the room has enough volume for it. Rome and Canton both follow the state code, and a city or county can add rules of its own, so the inspector always has the last word.
This is the part people skip, and it is the most common reason we get called to fix someone else's install. An oversized vent-free set fogs the windows, smells, and trips its own sensor. Measure the room, length by width by ceiling height, and bring the numbers.
Both kinds come in natural gas and propane versions, and a set is built for one or the other. Much of Floyd and Cherokee county outside town runs on propane, which is fine; the set just has to be ordered that way. A log set is not something to convert at the kitchen table. The orifices, the pressure, and on a vent-free set the oxygen sensor are all specific to the fuel.
Vent-free, clearly. The heat that would have gone up the flue stays with you, and a properly sized set will warm the room it sits in. The trade is that everything the flame produces stays in the room too, including water vapor. Some people notice the moisture, and people with asthma or other breathing trouble often prefer a vented set or a sealed insert instead. Manufacturers also limit how long a vent-free set should run at a stretch, and that is worth reading before you buy.
Vented sets are for atmosphere. They throw some warmth at the hearth, but with the damper open the room does not gain much. If real heat is the goal, a gas insert beats either kind of log set, and we would rather say that up front than sell the wrong thing.
Real Fyre builds vented and vent-free sets, and their vent-free burner systems are the ones we reach for when a room needs real heat from a closed fireplace. White Mountain Hearth, Empire's hearth line, makes both as well, in refractory cement and in lighter ceramic fiber logs. Both burn live in the Rome and Canton showrooms, so you can stand next to a vented set and a vent-free set and see what each one actually looks like before you choose.
Our own crew sets the burner, places the logs exactly where the manufacturer's diagram puts them, and tests the pilot and the safety shutoff. Log placement is not cosmetic: a log that blocks a flame port makes soot, and on a vent-free set it can trip the sensor. On a vented set we clamp the damper open. After that, an annual service keeps the ports clean and the sensors honest, which is what prevents the January phone call.
If you are weighing the two, the showroom is the fastest way to settle it. Bring the list above, and we will tell you which one your fireplace can take.
Sources
Rules change. This is where they stood when we published, and it is not a substitute for your installer or your local inspector, who have the last word on your fireplace.
See both burning
Both showrooms keep sets of each kind lit, so you can stand next to them and see the difference before you choose.