Gas fireplace vent question.

What would cause this gas fireplace to produce this “soot”. Also, from what I have read, this installation is pretty common for a gas fireplace (18" below the soffit).
Any comments are appreciated.


I have seen this soot pattern…
Is the Fireplace Natural Gas or LP?

Natural gas.

Bad air / fuel mix is my first thought and now I am trying to remember if the vent is allowed that close to a soffit opening.

Have not seen them that close yet on an inspection.

Are you sure they did not burn wood?

Tim ,hit this link for your answer on the soot.

Vertical clearance to unventilated soffi t - 12 in. (30 cm) minimum. **
Guess your OK

I would be concerned about the window.
I think most MFG. say 36 inches from windows or doors.

From Heatilator PDF on install clearance…

B Clearance to window or door that may be opened – 10,000 BTUs
or less, 6 in. (15 cm) minimum; 10,000-50,000 BTUs, 9 in. (23 cm)
minimum; over 50,000 BTUs, 12 in. (30 cm) minimum. *

But sections of that soffit are ventilated.

A bad air/fuel mixture and lack of service would be my guess at the problem.

Wow, thanks Bob.

Artificial logs or the medium for the esthetic fire can be one possible culprit here.
Natural gas well leave a residue.
All gas fireplaces leave a residue.
To what degree?
Are the components dirty?
Pilot assembly.
Propane fireplaces.

Natural gas fireplaces.
Are the components dirty?
The ignition source is important.
Maintain clean , good color and size of pilot lame is visible…

Check the logs if not placed right it will soot.

Exactly as Wayne said. Very simple

Thanks all!
Merry Christmas

Happiest of holidays to you and yours.

I would agree with the logs or fake embers impinging on the flame can cause this. If they are sealed and the glass is all black that usually goes along with a bigger than normal issue. All gas fireplaces can produce some soot but the more yellow the flame is the more soot likely.