Short answer
Before relighting a gas fireplace that’s been idle for years, shut off the gas, inspect and clean the unit, verify the venting is open and unobstructed (or confirm it’s a vent-free model), test for gas leaks, check the pilot/ignition components, ensure carbon monoxide detectors are working, and only then follow the manufacturer’s lighting instructions. If anything looks damaged, you find a leak, or you’re unsure about venting or gas pressure, call a qualified technician.
Why this matters
Gas fireplaces are reliable, but long periods of disuse can lead to blocked vents, spider webs in burner orifices, loose connections, failed gaskets, and stuck valves. Lighting a neglected unit without checks can cause sooting, poor combustion, carbon monoxide issues, or a gas leak hazard.
Tools and materials
- Flashlight and small inspection mirror
- Vacuum with soft brush attachment
- Soft paintbrush and microfiber cloth
- Compressed air canister (or low-pressure air)
- Screwdrivers (Phillips/flat), small adjustable wrench
- Leak detection solution or dish soap/water in a spray bottle
- Fresh batteries (AA/AAA) for remotes/receivers/igniters
- Non-ammonia ceramic glass cleaner (fireplace-rated)
- Mask and safety glasses
- CO detector (test button functional)
- Fire extinguisher (ABC) nearby
Step-by-step checklist
1) Identify your unit and shut off gas
- Find the data plate (usually in the control compartment) for model/type: direct-vent, B-vent (natural draft), or vent-free.
- Turn the main gas shutoff to OFF. If a manual shutoff isn’t visible within 6 ft of the unit, locate the upstream valve.
2) Clear the area and do a visual inspection
- Remove decorative items. Keep combustibles the required distance from the opening and surround.
- Check the glass for cracks and the door latch/gasket condition (rope gasket on some models). Replace if damaged.
- Confirm logs or media are intact and match your model. Misplaced logs can cause sooting.
3) Check and clean the venting (skip this section for vent-free)
- Direct-vent: Inspect the exterior termination. Remove nests, leaves, and debris. Ensure cap is intact, screen clear, and both intake and exhaust aren’t blocked.
- B-vent: Look from below and at the roof cap if accessible. If you suspect any collapse, corrosion, or bird nests, stop and schedule a chimney/vent inspection. B-vent relies on proper draft.
4) Open the firebox and clean
- Remove the glass (only when cool) per the manual. Lay it on a towel. Clean with fireplace glass cleaner—never ammonia or abrasives.
- Gently remove logs/media. Photograph placement first to ensure correct reassembly.
- Vacuum the firebox and burner tray with a soft brush. Use compressed air to clear burner ports and the pilot assembly. Don’t stick wires or needles into orifices.
- Wipe dust from the thermocouple/thermopile and flame sensor.
5) Inspect controls and wiring
- Check that the pilot tubing, thermocouple/thermopile leads, and valve connections are snug but not overtightened.
- If you have an IPI (intermittent pilot) or battery-backed ignition, replace batteries in both the remote and receiver/control box. Verify any 120V plug for blowers is live.
6) Reassemble and verify log placement
- Reinstall logs exactly per diagram. Incorrect placement restricts flame and causes soot.
- Reinstall the clean glass and ensure the gasket seals evenly.
7) Turn on gas and leak test
- Open the manual gas shutoff slowly. Spray leak solution on each accessible joint and the valve connections. Watch for bubbles for at least 30–60 seconds.
- If bubbling occurs: turn gas OFF, ventilate, and call a pro. Don’t attempt to light.
8) Test CO detectors
- Press test buttons on CO alarms on the same level and near sleeping areas. Replace units older than 7–10 years.
9) Light the pilot and burner per the rating plate
- Follow the lighting instructions on the appliance:
- Set control to PILOT, press and hold, ignite with the piezo or manual lighter as instructed, and hold 30–60 seconds until the pilot stays lit.
- Switch to ON. Use the switch/thermostat/remote to start the main burner.
- Observe the pilot: it should envelop the thermocouple/thermopile by about one-third to one-half of the flame.
10) Check flame quality and operation
- Main burner flames should have a blue base with soft yellow tips, stable and not lifting or roaring. Heavy orange, lazy, or sooty flames indicate aeration or placement issues—shut down and correct or call a pro.
- First burn after a long idle can smell and smoke slightly as dust burns off. Open a window and run 30–60 minutes.
Typical specs (always verify your manual)
Natural gas manifold pressure: ~3.5" w.c.
LP (propane) manifold pressure: ~10" w.c.
Natural gas inlet pressure: 5–7" w.c.
LP inlet pressure: 11–13" w.c.
Glass surface temps: can exceed 400°F—use a barrier if children present.
Pressure checks require a manometer and should be done by a licensed tech.
Safety and best practices
- If you smell gas, hear hissing, or the leak test bubbles, don’t light. Shut off gas, ventilate, and contact the gas utility or a pro.
- Keep a metal screen or manufacturer barrier in place. Hot glass can cause severe burns in seconds.
- For vent-free units, crack a window during the first hour of operation and ensure the ODS pilot flame is clean and sharp.
- Replace any cracked glass, frayed gaskets, or corroded vent components before use.
Common mistakes to avoid
- Using household glass cleaner on ceramic fireplace glass (leaves film and can etch)
- Incorrect log placement leading to soot and tripped CO alarms
- Skipping the exterior vent check (direct-vent caps often clog with lint or nests)
- Poking burner ports with pins (can deform orifices)
- Ignoring dead batteries in IPI systems—no spark, no light
Time and cost
- DIY cleaning/inspection: 1–3 hours. Materials: $15–40. Leak detector solution: $5–10.
- Professional service/tune-up: typically $150–300. Chimney/vent inspection or sweep (B-vent): $150–300.
When to call a professional
- You have any leak, damaged glass/gasket, corroded vent, or unknown model/log placement
- Pilot won’t stay lit after cleaning (possible thermocouple/thermopile or gas valve issue)
- Sooting, persistent odor, or poor flame shape after reassembly
- You need gas pressure adjustments or vent/liner repairs
A careful inspection, a good cleaning, and a proper leak test go a long way toward safe, trouble-free operation. If anything feels off, pause and bring in a pro—gas and venting aren’t places to guess.