My in laws furnace got red tagged yesterday for having 636 vent from two different suppliers ,one has blue writing on it the other has red writing .I have never seen the red one before and I cant make out any of the writing in the picture .does anyone know what this is about ?He used code 4.5.2 as the reason.
4.5.2 is covers pretty much everything that's deemed a hazard.
Unfortunately you cannot mix pipe from different manufacturers. So you cant mix IPEX (blue writing) with Royal York (black writing) and so on. Not on exhaust anyway. Odds are the installers have connected new pipe (blue writing) to old pipe that was there for the previous furnace (red writing) and well ... that's that.