Hole in exhaust pipe

questions

<span style="font-size:12pt">I have a high efficiency Carrier furnace, installed in 2008. I just noticed that there is a ¼ inch hole drilled into the side of the PVC exhaust pipe. It looks deliberate, but non-expert-me doesn’t think we should have exhaust entering the house. Is this hole there for a reason?  see atached photo</span>

Bob Harper

test hole

Probably a test hole for combustion analysis. See if there isn't one on both the intake and exhaust. Should be sealed with a plug or RTV silicone.