For a vented gas log set in a masonry fireplace, yes. A fixed opening has to stay in place so exhaust from the burning logs can never collect in the room, day and night, not only while the logs are lit. Most installation manuals call for the damper to be removed outright, locked open with a clamp, or held at a set minimum gap, and that instruction traces back to the National Fuel Gas Code rather than to habit. In Cherry Hill and Haddonfield, where plenty of prewar and postwar masonry fireplaces are still in use and heat comes mostly from natural gas across both towns, this question comes up often once a homeowner realizes the damper handle no longer moves the way it used to before the logs went in.
Vented sets need a fixed opening with no exception
A vented gas log set burns with its exhaust routed up the flue, the same path smoke would take from a wood fire. If the damper closes even partway while the burner runs, combustion byproducts have nowhere to go but back into the room. That is the reason the opening gets fixed rather than left on a lever a houseguest or a curious grandchild could bump closed. A ventless set works on a different principle and is not what this post covers, since the two systems are built around opposite assumptions about where the exhaust goes, and the fireplace in front of a homeowner either has one or the other, not a mix.
Where the label is and why it rules
Every gas log set ships with a manufacturer's plate, usually a small metal or foil label fastened near the burner pan or on the frame holding the logs in place. That label names the minimum damper clearance the set was tested with, and it is the document that governs the installation, not a general rule of thumb passed along by whoever sold the logs. A set that came with the house, installed by a previous owner with no paperwork left behind, still has that plate somewhere under or beside the burner. Finding it before assuming a clamp position is correct is worth the five minutes it takes to look, since two sets that look alike on the showroom floor can call for different minimum openings.
What a damper clamp holds
The clamp fitted to a damper for a gas log installation is a mechanical stop, usually a bracket or a bar that keeps the damper blade from swinging past a set point toward closed. It is not a convenience feature and it is not meant to come off once the logs are installed, even for a homeowner who wants to close the fireplace up tight during a cold snap. Removing the clamp to seal the opening defeats the reason it was installed in the first place, and a technician doing Chimney Repair who finds a clamp missing or bent out of position flags it before any other work on that fireplace continues, since the fix is resetting or replacing the clamp before the logs are lit again.
The conditioned air a fixed opening lets out
A damper locked open is also a damper that never stops venting warmed or cooled house air up the flue, which is the tradeoff that comes with a gas log installation in a masonry fireplace. That loss runs in the background of a utility bill in a way that is easy to miss, since nothing about it looks like a problem day to day. Homeowners who want to limit that loss sometimes ask about a top-sealing damper system engineered to work with the fixed minimum opening a gas log set needs, which is a conversation for Chimney Repair rather than something to improvise by propping the existing throat damper differently than the clamp allows.
Smoke or soot in the room is a draft fault, not normal
A damper fixed open is not a guarantee that exhaust always finds its way up and out. If soot streaks the glass doors, a burning smell lingers in the room, or smoke drifts back toward the mantel while the logs run, something in the flue's draft is working against the opening rather than with it, a blocked cap, a liner issue, or a flue sized wrong for the logs installed in it. The fix is not adjusting the damper further open, since the clamp already sets the minimum the manufacturer tested. The set stays off until a technician doing Chimney Cleaning or Chimney Repair finds what is interrupting the draft, because a fireplace that pushes exhaust into the room instead of up the flue is not a fireplace to keep using while the cause goes unaddressed.
Why the flue above gas logs still gets a yearly look
A fireplace burning gas logs produces far less soot than one burning wood, and that leads some homeowners to assume the flue above it never needs attention once the logs are in. Birds and squirrels do not check what fuel a chimney burns before building a nest in an uncapped flue, and a gas appliance's exhaust still carries moisture that can affect a liner over the years the same way it would above a wood fire. An annual look at the flue above a gas log installation, checking the cap, the liner, and the clamp holding the damper at its set point, catches a developing blockage or a loosened clamp well before either one turns into smoke in the living room.