Fireplaces and flues
Gas fireplaces and inserts, the vent checks a sweep does and the gas work we refer out
We inspect gas fireplace, gas insert and log set venting across the Portland metro and refer burner work to a gas fitter. The usual faults are a nest in the cap, condensate eating a liner, or a log set with no damper stop.
Updated
What a gas fireplace and insert is and how it vents
A gas fireplace burns natural gas or propane behind glass or in an open firebox and sends its exhaust out through a metal vent rather than a brick flue. A gas insert is the same appliance built to slide into a masonry or factory-built fireplace.
Three venting styles cover the units we see. A direct vent unit is sealed behind glass and breathes through a coaxial pipe or a pair of liners. A B-vent unit draws room air up a double-wall pipe, and a vented log set uses the masonry flue it sits under.
Census figures put close to a third of Washington County housing and a quarter of Clackamas County housing at 2000 or newer, and those subdivisions are where the direct vent box in a framed wall lives. Older Portland houses meet gas as a log set in the original brick fireplace or an insert added later.
How to tell what you have
Four tells sort a direct vent unit from a B-vent unit from a log set without a ladder.
- A fixed glass front held by clips means direct vent; a door that swings open or no glass at all means B-vent or a log set.
- Outside, a louvered hood on the siding near the fireplace is a direct vent termination; a round pipe with a cone cap above the roof is B-vent.
- On a brick chimney, a stainless top plate with a cap and two collars means an insert on liners; a bare clay tile means a log set.
- Ceramic logs on a burner tray with a gas key in the hearth, under a damper handle clamped open, is a log set in a masonry fireplace.
What you will find in Portland homes
Here are the gas units we meet around Portland and the venting each depends on.
| Type or model | Era | Notes |
|---|---|---|
| Vented gas log set in a masonry fireplace | Retrofit | Burns under a damper clamped open, so the flue is open all year; soot from the logs and rain through an uncapped tile land on the smoke shelf. |
| B-vent gas fireplace | Older gas fireplaces | Double-wall pipe fed by room air; the draft hood spills when the pipe is cold or blocked, so the cap screen and the joints get checked yearly. |
| Direct vent gas fireplace in a framed chase | Late 1980s to current | Sealed glass and a coaxial pipe out a wall or through the roof; the failures are a flat gasket, a crowded hood and a rusted chase cover. |
| Direct vent gas insert in a masonry fireplace | Current, retrofit | Two flexible liners run the old flue to a sealed top plate and cap; a liner that stops short or kinks dumps exhaust into the chimney. |
What goes wrong and what fixes it
The gas fireplace and insert problems below each name their service.
-
A vent nobody has looked at since the unit went in
A Level 2 inspection with the camera down the vent or liners, plus the termination and the firebox side, with photos sorted by trade Chimney Inspection, from $129
-
A termination cap or screen that is missing, crushed or packed with a nest
A listed cap matched to the vent type, screened against birds and open enough for the exhaust Chimney Cap Installation, from $299
-
Soot, leaves and rain debris on the smoke shelf above a log set
The open flue swept and the shelf vacuumed, then a cap on the tile Chimney Sweep, from $249
-
A log set burning under a damper that still closes
A damper stop fitted so the flue cannot be shut while the logs can be lit Damper Repair and Replacement, from $149
-
An insert venting into a cracked tile or unlined flue with no liners of its own
Two liners run to the top, wrapped in insulation where needed, under a sealed plate and cap Chimney Liner Installation, from $1999
What a gas fireplace vent inspection covers
A gas vent inspection covers the termination and vent run, the chase or chimney around it, and the firebox side, in that order.
The termination and the run
At the roof cap or wall hood we check for the listed cap, a clear screen and clearance from siding, a deck or a window. B-vent pipe is checked joint by joint through the attic, and on an insert the camera goes down both liners to the collars.
The chase or the chimney
A framed chase gets its chase cover checked for rust and standing water; a masonry chimney gets its crown, tile and brick looked at, since an insert does nothing to stop rain on the stack around it.
The firebox side
With the unit off we look at the glass gasket, the logs against the burner, soot on glass or log tips and the damper stop on a log set. Burner, pilot and valve work is a gas fitter's job.
Why a gas fireplace still needs a yearly vent inspection
The national chimney standard calls for every chimney, fireplace and vent inspected each year, gas included, and the faults on a gas vent are the quiet kind nobody notices.
Burning gas makes water vapor that carries acids. Where a liner or pipe never gets fully warm it condenses, the acid works on aluminum, steel and mortar, and the damage shows at the cap before the room knows.
A log set in an unlined Portland fireplace is the case to think hardest about, since its exhaust runs up bare brick and wets the joints from inside; a liner sized to the log set puts that exhaust in metal.
Carbon monoxide and the gas fireplace, what to do and when
When a carbon monoxide alarm goes off while the gas fireplace is running, or anyone in the room gets a headache or dizziness that eases outdoors, leave the house first and call 911 from outside.
A gas fireplace or insert counts as a carbon monoxide source under Oregon law, like a gas furnace, and a blocked termination, a spilling draft hood or a flat gasket each puts exhaust in the room.
Keep a working alarm on that floor; Oregon requires alarms covering the sleeping areas before a house with a fuel-burning appliance changes hands. Soot on the glass or flames rolling past the opening mean the unit stays off until a gas fitter and a sweep have looked.
Gas fireplace and insert questions
Does a gas fireplace need a chimney inspection if it never burns wood?
Yes, once a year, because the national chimney standard covers vents as well as chimneys. A gas fireplace makes no creosote, but its exhaust is wet and acidic, its cap collects nests, and a flat gasket or a separated pipe puts exhaust in the room with nothing to see or smell.
What does a chimney sweep check on a gas insert that a gas fitter does not?
The venting and the chimney around it. That means both liners from the top plate to the insert collars, the plate seal and cap, the crown and brick of the old stack, and any chase the vent passes through. The gas fitter owns the pilot, valve, burner and gas line.
Can a gas insert go into the brick fireplace of a 1920s Portland house?
Usually yes, on two liners run the full height of the chimney, once a camera inspection shows the old flue can take them. The liners carry exhaust and intake air in metal, so the old brick stops being the vent path, and Portland requires a permit for the installation.
My gas fireplace will not light. Is that a chimney problem?
Almost never; a pilot that will not hold or a burner that will not catch is gas-side work for a gas fitter. The vent side shows up differently: a unit that lights and then dies after a few minutes can be a blocked termination starving the flame.
Is it safe to run vented gas logs with the fireplace damper closed?
No. Vented gas logs send their exhaust up the chimney, and a closed damper sends it into the room, which is why a log set is installed with a damper stop that holds the flue open. Keep the logs off until a stop is fitted, and put a carbon monoxide alarm on the same floor.
Related pages
Gas fireplace and insert calls near you
Gas fireplace and insert work has taken us to Oregon City, Sellwood-Moreland, Wilsonville and the rest of the metro, and the posted price is the same at every address.
Other fireplace and flue types
Ready to book a sweep?
Call with what the fireplace is doing, or text a photo of the opening and one of the chimney top, and we will name the service and its posted price before we come out.