Reviving this thread after a while on idle!
I am about to cap the metal stud box I built for the future mantel. Its getting mildly cold here in Montreal in the morning so Ive decided to prep the fireplace for upcoming winter by cleaning it with a Vacuum, etc... I have never used the fireplace since I moved in (almost 2 years ago) but I knew it was working because when I purchased the house, the previous owner had it on. Also, there are signs of usage..
One day, I started the pilot light around noon, waited for a few minutes to make sure everything was fine and stable, then I left the house. I came back around 4pm. When I entered the house, I was greeted by a mild (not so strong but very noticeable) smell of what appeared to be natural gas. I immediately shut off the pilot and closed the main yellow gas valve. I opened all windows and patio doors to evacuate the smell as soon as possible. The smell seemed to come out of the top louver. I smelled inside the bottom cavity where the "equipment" is located (gas valves, thermocouple, pilot valve, etc) but nothing there. Nothing behind the fireplace, and nothing inside the walls.
I then called a gas appliance technician and booked a service call. He came a few days later to look at the fireplace but didn't find anything wrong. He brought a natural gas detector with him (sniffer) but the device didn't register anything (literally 0ppm). To him, the smell coming out of the top louver is not natural gas. To me, whats coming out of the louver smells like garlic or maybe like moly grease.. Difficult to explain but it doesn't smell like burning dust or heat at all...
He did a thorough cleanup and tested everything. He even used a BBQ lighter to find out if there were gas leaks anywhere in the equipment. According to him, its totally safe to do so, since there are no oxygen in the gas line, as well as the gas pressure forces the flame out, so no chance of fire returning to the main or exploding.. I am not convinced... I must say, I was on "alert"
Anyways, after about half hour looking at the fireplace, he admitted that he couldn't find anything. Other thing he said, there would be no chance of some gas not burning inside the firebox as the pilot flame would burn any residual gas.. The only chance for natural gas to leak and be smelled is from the control equipment and gas pipes at the bottom of the fireplace where there are no flame to burn the gas, but then we would smell it coming from there..
I noticed that when the fireplace was really running (real flames) the "gas" smell seemed to considerably reduce... Almost to nothing. The tech had some gas vented on purpose to have me confirm it was what I smelled. It was, but much stronger.
I has a few people coming over and they confirmed they can smell something like natural gas. According to the tech, it is absolutely safe to use the appliance. So I tried to leave the pilot on for a few days, and purchased a good natural gas+CO detector and installed it right on top of the fireplace. It didnt register anything.
Long story short:
Gas-like smells coming out of top louver ONLY when on pilot
Sniffers and detectors not reading anything
No gas smell when real flames
No apparent or detectable leaks anywhere
Abnormal smell confirmed by several people (including neighbors having the exact same appliance confirming my fireplace release a smell that theirs dont
What next????? Everything seems to contradict. I must admit, I am clueless... Should I rely on equipment or my (our) nose(s)?