Use this gas fireplace glossary to look up the terms you’ll see on product pages, rating plates, and in owner’s manuals. It covers venting, ignition, fuel types, and replacement parts for gas fireplaces, inserts, and gas log sets. If you’re shopping for a part, start with the fireplace’s make, model number, and fuel type so you can check compatibility before ordering.
Common Gas Fireplace Terms
- Comparing venting options? Start with direct vent, natural vent, and vent-free.
- Updating an existing fireplace opening? Compare a gas fireplace insert and a gas log set.
- Trying to identify your ignition system? Look up standing pilot, intermittent pilot ignition, and millivolt.
- Reading a spec sheet? Check BTU input, heat output, and inches of water column.
Gas Fireplace Terms A–Z
A
Air shutter. An opening at the burner inlet that controls how much air mixes with the gas before combustion. If the flames look different than usual, check the manual and have a qualified technician assess the burner settings.
B
BTU input. The rate at which a fireplace uses fuel energy, typically listed in British thermal units per hour (BTU/h). A product page may shorten this to “BTU.” Check whether the number refers to fuel input or heat output before comparing models.
Burner. The component that distributes gas through openings where the flames form. A burner assembly is designed for a particular appliance, fuel, and control configuration, so match replacements to the fireplace model.
C
Clearance to combustibles. The minimum separation the manufacturer requires between the fireplace or vent and materials that can burn. Check the installation manual for the specific surface you’re planning around, such as a mantel, sidewall, or framing.
Conversion kit (NG/LP). A model-specific kit for changing a compatible appliance from natural gas to propane or from propane to natural gas. Confirm that the manufacturer allows the conversion and specifies a kit for your model and the direction of the conversion. Have a qualified technician perform the work.
D
Damper. A movable plate in a fireplace chimney or flue that regulates the opening. Some vented gas log sets require a damper clamp or stop to prevent full closure. Follow the requirements for your specific log set.
Direct vent. A system that draws combustion air from outdoors and sends exhaust outdoors through a dedicated vent. A direct-vent fireplace uses a sealed combustion chamber. Vent routing and approved components depend on the model.
E
Electronic ignition. A system that uses an electronic control to start the fireplace’s ignition sequence. Intermittent pilot ignition is one type. Check the model’s specifications for its power source, compatible controls, and battery backup options.
Ember media. Material placed in designated areas of a gas fireplace or log set to create the look of glowing embers. Use the type, amount, and placement specified for your appliance.
F
Firebox. The chamber where the burner and flames are located. When shopping for an insert or gas log set, compare the measurements required by the product manual with the dimensions of your existing firebox opening.
Fire glass. Decorative glass made for use as fire media. Use it only in fireplaces designed for it and follow the manufacturer’s directions for placement and quantity.
Flame sensor. A component used by the ignition system to verify that a flame is present. How the system senses flame and responds to flame loss depends on the fireplace’s design.
Flue. A passage that carries combustion exhaust outdoors. An existing chimney flue may be part of a vented gas log installation or serve as a route for approved liners on certain gas inserts.
G
Gas fireplace insert. A self-contained gas appliance designed to fit inside a compatible existing fireplace opening. Check the required opening dimensions, fuel type, and venting before choosing an insert.
Gas log set. A gas burner and decorative logs designed for installation in a compatible firebox. Gas log sets are available in vented and vent-free configurations. Check the log set’s installation requirements and local rules before choosing one.
Gas valve. The component that controls gas flow within the appliance. Replacement compatibility depends on the fireplace model, fuel type, and ignition system. See also shutoff valve.
H
Heat output. The rate at which the appliance delivers useful heat, often expressed in BTU/h. Compare output with output when shopping. A published BTU input rating describes fuel energy used by the appliance.
I
Ignition module. An electronic control component that manages the ignition sequence on compatible fireplaces. Confirm the model and part number when replacing a module or checking whether a remote or Wi-Fi accessory will work.
Inches of water column (in. w.c.). A unit of pressure you may see in a gas fireplace manual. The listed values can refer to different points in the system, such as the valve inlet or burner manifold. A qualified technician uses the specifications for the exact model and fuel type.
Inlet pressure. The pressure of the gas supplied at the appliance valve’s inlet. See also manifold pressure.
Intermittent pilot ignition (IPI). An electronic ignition system that lights a pilot when the fireplace calls for a flame. The pilot then lights the main burner. Some systems also have a continuous pilot setting. See also standing pilot.
K
Key valve. A manually operated gas valve that uses a removable key. If you’re replacing a key, flange, or valve, identify the existing component and how it’s used in your fireplace setup before ordering.
L
Liquid propane (LP). A fuel stored as a liquid under pressure and supplied to a compatible fireplace as a gas. Look for the LP designation on the rating plate or product specifications when checking fuel compatibility.
M
Manifold pressure. The gas pressure on the burner side of the appliance valve at the point specified by the manufacturer. Manuals may list this alongside inlet pressure, with separate specifications for natural gas and propane.
Media. Decorative material such as logs, ember material, or fire glass. Use the media and placement instructions approved for your model, especially around the pilot and burner openings.
Millivolt system. A control system commonly found on standing-pilot fireplaces. A thermopile heated by the pilot generates the small voltage used by the control circuit. Check the model’s requirements before buying a switch, thermostat, or remote.
N
Natural gas (NG). Fuel typically supplied through a utility gas line. If a fireplace is listed for NG, check the rating plate and manual before ordering gas controls or considering a fuel conversion.
Natural vent (B-vent). A venting design that uses natural draft to carry exhaust outdoors, typically through a vertical vent. The appliance generally draws combustion air from the room. Check the model’s instructions for the required vent system.
O
Orifice. A precisely sized opening that meters gas into a pilot or main burner. The correct orifice depends on the appliance and fuel type. Have a qualified technician handle replacement or conversion.
Oxygen depletion sensor (ODS). A pilot safety system used on vent-free appliances. It is designed to shut off gas if oxygen levels near the pilot drop below the system’s operating threshold. Keep the manufacturer’s installation and operating requirements in view when comparing vent-free models.
P
Pilot assembly. The group of parts that lights the main burner and supports flame sensing. Its components vary by model and may include a pilot burner, igniter, thermocouple, thermopile, or flame sensor.
Pilot light. A small flame that ignites the main burner. A standing pilot stays lit while the appliance is in pilot mode. An intermittent pilot normally lights during the ignition sequence.
R
Rating plate. The appliance label that identifies details such as the model, serial number, fuel type, and input rating. Check the manual for its location. A photo of the label can help when identifying replacement parts.
Regulator. A device that controls gas pressure. Depending on the setup, pressure regulation may be part of the gas supply system, the appliance, or both. Follow the appliance specifications when identifying a replacement.
Remote receiver. The component that receives commands from a compatible handheld transmitter. Before ordering a fireplace remote, check both the receiver model and the fireplace’s control system.
S
Shutoff valve. A valve used to isolate the gas supply to the appliance. The fireplace’s gas control valve handles gas flow during operation. Check the appliance documentation if you’re unsure which component you’re looking at.
Standing pilot. A pilot flame that stays lit between calls for the main burner while the appliance is in pilot mode. Standing-pilot fireplaces may use millivolt controls. See also intermittent pilot ignition.
T
Thermocouple. A sensor that generates a small electrical signal when heated by the pilot flame. In systems that use one, that signal helps keep the pilot safety valve open while the pilot is lit.
Thermopile. A group of thermocouples that generates a higher voltage than a single thermocouple. In a millivolt fireplace, it can supply power to the main burner control circuit. Some pilot assemblies use both a thermocouple and a thermopile, so check the parts diagram before ordering.
V
Vent termination. The approved fitting at the outdoor end of a vent system. It may be mounted on an exterior wall or at the roof, depending on the appliance and vent design. Use the fireplace manual to identify compatible gas fireplace venting components.
Vent-free (ventless). A gas appliance designed to operate without a dedicated exhaust vent to the outdoors. The unit uses room air and releases combustion products into the room. Check local restrictions and the manufacturer’s room and installation requirements before choosing one.
Vented gas log set. A gas log set designed to exhaust through a compatible fireplace chimney. Follow the log set’s instructions for the fireplace, flue, and damper.
W
Water column. A pressure measurement commonly shown as inches of water column on gas fireplace rating plates and in installation manuals.
Frequently Asked Questions
What’s the difference between a gas fireplace insert and a gas log set?
A gas fireplace insert is a self-contained appliance that fits into a compatible existing fireplace opening. A gas log set is a burner and decorative logs installed inside a compatible firebox. Compare the opening dimensions, fuel type, and venting requirements before choosing either one.
Where do I find my gas fireplace’s model number and fuel type?
Look for the appliance rating plate. Your owner’s manual can help you locate it. Record the model number, serial number, and fuel designation, usually NG for natural gas or LP for propane, before shopping for replacement parts.
Can I use any gas fireplace remote with a millivolt system?
Choose a remote and receiver that are compatible with your exact fireplace and control system. If you’re replacing only the handheld remote, check that the new transmitter will pair with your existing receiver.
Need Help Matching a Gas Fireplace Part?
Send our product specialists the fireplace make, model number, and fuel type. A photo of the rating plate and any part number on the original component can help us narrow down the options. If you’re still comparing appliances, browse our gas fireplaces by style and installation type.
