Haven’t ran into this type of venting before. Is the open PVC vent correct on the left?
It’s for combustion air.
Looks like a standard installation
It’s acceptable as long as enough “fresh” combustion is being provided at interior. I always recommend to extend the pipe to the exterior.
I figured it was for combustion air, but there was a slight gas smell. The other PVC pipe vented to the exterior.
Depends on the manufactures installing instructions, some allow it and some do not but either way, there should be no gas odor.
This is correct. Different manufacturers have varying installation instructions (some need to come from the exterior) but gas smell isn’t included.
Most manufacturers say a key word there usually “may”. Combustion air “may” be done this way. It’s up to your AHJ and around here most of them say NO WAY, pipe it in from outside. If I remember correctly Coleman mostly used a sealed combustion. So I little rough light off or out of plumb unit and it will smell of gass from time to time. I see the installer did not perform a combustion analysis on it. They might have set the gas pressure by the label and picked a wanted airflow from the manual. Do a combustion analysis, set the gas pressure, test CO and believe it or not you can get the correct fan speed selected this way. The units last a lot longer when setup this way