Certainly you can replace the batteries in perfect safety. (I’m assuming that this is a commercial device of some kind with a UL – Underwriters’ Laboratory – on it in some place. That UL sticker is an indication that the product has been designed with consumer safety in mind, and as long as the assembly is in good shape, not broken, cracked, corroded, burnt, etc., then it’s “not going to hurt you”, even if it doesn’t still work.) If it’s a homemade device of some kind or if it’s damaged in any way, then I withdraw that comment about it being safe. It might still be, but it’s likely to be unsafe if it’s in a damaged condition.

If the thing has this kind of battery starter, then I would doubt very much that it has a pilot light. It’s going to be one or the other, I think: electronic ignition OR pilot light, not both.

@CWOTUS That does help me, because it confirms my guess that I don’t have a pilot light. Is it possible there is a gas shut off somewhere? Obviously the light switch controls the gas and triggers the flint to light, but would there be a way to turn off the gas inside the fireplace to override the wall switch?

I’ m just guessing but the batteries may be a back up in case the power fails. Our gas fire had button you pressed that created the spark that ignited the gas. If you have the make and model number of the fire you may get a manual online. For example Heatilator.

If there is a gas shut off, and it is anything like my gas fireplace, there should be a valve in a hole in the floor close to the front of the fireplace. It takes a key to turn it on to allow gas to flow to the logs. Mine has a control box that uses 4 AA batteries and is for the remote control that turns the logs on. There is a gas control box (again this one is for mine) that has controls like my water heater. It lights a pilot light. The switch on the wall for mine bypasses the remote control and turns the logs on regardless of the room temp.

I have a key that I thought maybe opened the chinmey? We don’t have a chimney up through the roof, it just vents through an exterior wall to the outside. Maybe that actually opens the gas? There is a place for the key below the wall switch.

There is actually an on off switch inside the fireplace I just noticed.

Ugh, I am too nervous.

The FP gas key should be a square socket on a longish stem that turns a valve that is recessed in the face of the wall. Then before that in the gas piping there should be another gas valve that shuts it off to the entire unit. Should be red, or green i forget which. Both valves have to be opened to light the burner. The batteries could be for a remote receiver?

@woodcutter The key is square. So is the “chimney” always open then? Oh, a remote! Maybe? So, the light switch probably controls the flint and the gas? Meaning once the gas lines were opened, still the switch turns the flow of gas off and on. Like turning the nob on a gas stove.

I dont think the wall switch has anything to do with the gas. Gas valves are hand turned valves. That switch might be for a fan motor.

Modern gas appliances are generally so efficient that the exhaust gas is vented through PVC piping (“plastic”, to the lay person) because it’s not so hot that it will melt that. But that exhaust is still a potential carbon monoxide source, so you’ll want to be certain that the vent is open. (Sometimes birds build nests on the outlet, for example, or leaves can blow into the vent. If your vent outlet is screened on the outside, then those probably aren’t great concerns.)

There should not be a damper on that vent; it’s a free and unobstructed vent (or should be). Other respondents have told you correctly that the smallish key that you have is to open the gas line.

If I were you, I’d replace those batteries with fresh ones, open the gas line and give it a whirl. If the gas doesn’t ignite and you get a gas smell in the room, then turn if all off and get professional help with the setup. A “gas smell in the room” won’t hurt you; it’s not like you’re going to leave the gas on until you get a potentially lethal concentration (to asphyxiate residents of the dwelling) or create an explosive concentration, either. You’d be turning off the gas long before those are valid concerns.

This is essentially how to light the pilot in logs similar to mine. Youtube had several other kinds that I had never used before so have no experience with. Try turning the valve on the wall clockwise. This is usually the direction to close the gas off. If it turns easily, Try anti-clockwise until you hit some resistance. Then dig about in amongst the logs looking for knobs and switches. Usually there are instructions either on a sticker or embossed somewhere on operation of the pilot light (if there is one, most do). You needn’t be afraid of blowing anything up if everything is in reasonably good shape and you aren’t smoking. If you smell gas, turn the valve on the wall completely clockwise and air out the room. I would search youtube for a fireplace that looks like yours because there were a bunch of them.

Just sent this to LuckyGuy who will no doubt be able to help you.

@janbb Great idea. Although, I think @CWOTUS is probably on the spot with his last bit of advice.

All the answers have been very helpful though.

@JLeslie I was thinking call in a professional or LuckyGuy. I don’t like messing with gas. I’ve seen two houses blown up by gas. It doesn’t leave anything left.

@Adirondackwannabe A friend of mine charred her kitchen and a little bit of herself.

@JLeslie I like the idea of gas. It burns clean. But wow, you see a house leveled, with the biggest piece not more than 12 inches, and I think twice about it.

Oops! I am late. Yes there is a shut of valve that you can access with a square key – like an old skate key only longer . You might also have an additional shut off in the line going to the unit. that might be in the basement. You will be able to turn that one with a simple adjustable crescent wrench or even a hand lever.
The D batteries are for the ignition. It is wasteful to have a pilot light going all the time. To light them there is usually a button to push and hold which starts the gas flow and turns on the piezo ignitor. You will hear a clicking sound like a gas grill. That is the ignitor going. Once lit the heat from the flame tells the unit to keep gas flowing. If there is no heat, the gas is shut off.
You will not blow yourself up. expect to smell gas or the first 5 to 10 seconds until it lights. If you continue to get gas smell for a long time give up.
Do you have the model number somewhere.