Last year, we had problems with our gas furnace. A technician came in to fix the problem. While he was troubleshooting, he put a small hole in the flue pipe and inserted a small rod to read the flue temperature. After that, he put a small button like cover to close the hole.
Recently, last week I found out that the button cover was on the floor. I don't know when it fell. I put it back to cover the hole.
Can the harmful flue products like CO escape through such a small hole?
The small cover keeps on falling. Every day, I have to check this out. can this small hole be open for some hours without causing any harm to us?
Any idea? thank you.