How Fireplaces Work
Direct vent, pilots, BTUs, blowers — the education behind a confident purchase.
venting types
- What is a direct vent gas fireplace and how does it work?
- How does a ventless gas fireplace work without a chimney or vent?
- What is a B-vent (natural vent) gas fireplace?
- What's the difference between a direct vent and a B-vent gas fireplace?
- Do gas fireplaces need a chimney?
- How does the pipe-within-a-pipe (coaxial) vent on a direct vent fireplace work?
- What does "sealed combustion" mean on a gas fireplace?
- Can a direct vent fireplace vent horizontally through an outside wall?
- What is a power vent fireplace and when do you need one?
- Why doesn't a direct vent fireplace use air from inside the room?
ventless mechanics
- How does a ventless fireplace burn cleanly enough that it doesn't need a vent?
- What is the oxygen depletion sensor (ODS) on a vent-free fireplace and how does it work?
- Why do ventless fireplaces add moisture and humidity to a room?
- Why do vent-free fireplaces have room-size and run-time limits?
- What does a "vent-free approved" firebox mean?
gas logs venting
chimney anatomy
- What is a flue?
- What is a fireplace damper and what does it do?
- What is a chimney liner and what does it do?
- What does a chimney cap actually do?
- What is a chimney chase and a chase cover?
- What are the smoke shelf and smoke chamber in a fireplace?
- How does chimney draft work — why does smoke go up the chimney?
- What's the difference between single-wall and double-wall stove pipe?
- What is a chimney crown, and how is it different from a chimney cap or chase cover?
- What is a chimney balloon or flue plug, and how does it seal off an unused fireplace?
combustion air
ignition systems
- What is a standing pilot light and what does it actually do?
- What is a millivolt valve on a gas fireplace and how does it work?
- What is intermittent pilot ignition (IPI) on a gas fireplace?
- What's the difference between IPI and a standing pilot?
- How can a millivolt gas fireplace run without any electricity?
- Will a gas fireplace still work when the power goes out?
- How does a piezo igniter work?
- What is the battery backup on an electronic ignition fireplace for?
- What is flame sensing (flame rectification) on a gas fireplace?
- What is a cold-climate pilot setting on an IPI fireplace?
pilot components
gas valve fuel
- How does the gas valve in a fireplace work?
- What is an orifice, and why are natural gas and propane orifices different?
- What's the mechanical difference between a natural gas and a propane fireplace?
- What does a natural gas to propane conversion kit actually change?
- Why do natural gas and propane flames look different?
- Why does a gas flame burn blue instead of yellow?
- How do gas fireplaces produce tall yellow flames without making soot?
- What is incomplete combustion?
- What gas pressure does a fireplace need — what is manifold pressure?
ratings efficiency
- What does BTU mean on a fireplace?
- What's the difference between BTU input and BTU output?
- How many BTUs do I need to heat my room?
- What is AFUE, and do fireplaces even have AFUE ratings?
- What is a Fireplace Efficiency (FE) rating?
- Why are ventless fireplaces described as 99% efficient?
- How efficient are direct vent gas fireplaces?
- What's the difference between a "decorative" and a "heater-rated" gas fireplace?
- How do you figure out how much gas a fireplace uses from its BTU rating?
wood heat science
blowers fans
heat science
heat management kits
zone heating
fireplace anatomy
- What is a firebox?
- What is a hearth?
- What's the difference between a mantel and a surround?
- What is a lintel on a fireplace?
- What are the refractory panels (firebrick liners) inside a firebox?
- What is a fireplace grate for, and why do wood fires need one?
- What is a fireback?
- What is an ash dump in a fireplace?
- What is a gas log lighter (gas starter pipe) in a wood-burning fireplace?
fireplace types
- What is a zero-clearance fireplace?
- What's the difference between a masonry fireplace and a prefab factory-built fireplace?
- What is a fireplace insert?
- What's the difference between a gas insert and gas logs?
- What's the difference between a fireplace insert and a built-in gas fireplace?
- What is a freestanding gas stove?
- What's the difference between a wood stove and a wood-burning fireplace?
- What is a wood-burning fireplace insert and how does it work?
- What is a Rumford fireplace?
glass barriers
wood stove tech
- How does a modern wood stove actually work?
- What is secondary combustion — what are the tubes at the top of a wood stove firebox?
- What's the difference between a catalytic and a non-catalytic wood stove?
- What is the baffle in a wood stove?
- What does "burn time" mean on a wood stove?
- What does EPA-certified mean for wood stoves and inserts?
- What does grams-per-hour mean on a wood stove emissions label?
- What is an air wash system on a wood stove?
wood fuel basics
gas log construction
gas log media
remotes controls
- How does a gas fireplace remote control work?
- What's the difference between an on/off remote and a thermostatic remote?
- How does a gas fireplace wall switch work?
- Can a gas fireplace be controlled by WiFi or a smart home system?
- Can you connect a gas fireplace to a regular house thermostat?
- How does flame height adjustment work on a gas fireplace?
- What is flame modulation (turndown) on a gas fireplace?
electric fireplaces
- How do electric fireplaces work?
- How do electric fireplaces create the flame effect?
- What is a water vapor fireplace and how does it make 3D flames?
- Do electric fireplaces give off real heat?
- What's the difference between infrared and fan-forced heat in an electric fireplace?
- Do electric fireplaces need to be vented?
- Can you run an electric fireplace's flames without the heat on?
- What's the difference between a plug-in (120V) and a hardwired (240V) electric fireplace?
- How much heat does an electric fireplace actually put out — how do watts compare to BTUs?
- What's the difference between an electric fireplace insert and an electric log set?
conversions
see-through units
gas fire pits
- How does a gas fire pit work?
- What is a fire pit burner ring or burner pan?
- What is a key valve on a gas fire pit?
- What's the difference between match-lit, push-button, and electronic ignition fire pits?
- Why do propane fire pits need an air mixer?
- Why can't you use regular gravel or river rocks in a gas fire pit?