gas pipe clearance to flue?

Does anyone know the minimum clearnace of gas piping to a flue pipe? I had one today where the gas piping was touching the flue pipe. (see photo) I’m not sure of the proper clearance, but it didn’t look good to me. Thanks

Northwood 011.jpg

The flue (B-vents) generally requires clearances to “building materials,” which would include piping. But it’s not more of an issue simply because it’s a gas pipe.

As in clearance from the insulation and drywall and where is the fire-stop/flue collar?

What is the source of the moisture stain?

May have been trying for pre-ignition :shock:

This is a furnace flue pipe, not a chimney, so I wouldn’t think it needs fire stopping, but yes, I did note that is was touching attic insulation. (1 inch minimum to combustible materials) My specific concern was the gas pipe. I have never seen anything that requires a specific distance from a gas pipe, and maybe there isn’t one, but it seems like there should be. I suppose I invision a gas leak that catches fire from the hot flue pipe. Yikes!