I recently inspected a house that had this particular issue, in reality this is an issue on a lot of homes with a gas fireplace but this buyer was particularly concerned over this one. So I thought I would shed some light on this.
If you look at the picture where the gas line enters the firebox wall there is a small gap around the pipe. This should ALWAYS be written up as a defect if the fireplace is a wood/gas appliance.
Here’s the danger with this; when the wood is burning in the firebox and the flame is thirsty and starving for oxygen it will take it from any source it can get. Usually this is the room air but what happens in a well sealed and insulated home is the flames will try to creep inside this gap and follow the air along the pipes. This is due to a higher oxygen content over the room air that has been lowered by the burning fire.
What are the chances? Well the chances are less then every time but more then zero so it’s worth having this issue fixed or monitored if you intend on using it. It’s kind of like when Jim Carey tries to get a date in Dumb and Dumber “so you're saying there’s a chance!” A house fire is one of those things you don't want to leave to chance.
Bottom line here is it is cheap to fix and effective at reducing a fire hazard in the home, don't let it kill your new home but get it fixed so you don't risk a fire.
I am a United States Army Veteran with over 10 years construction experience prior to my service. After my time in the military I enrolled in InterNACHI's rigorous course work to become a certified member and prepare for the National Home Inspectors Exam. I continue to push inspection courses and education, attaining and exceeding the required continuing education courses