I believe that flexible gas line (plastic coated) has an interior core of aluminum, not steel, hence the flexibility. If that is indeed the case, the temperature could get high enough to melt it. BOOM!
I spent 5 years inspecting water main and water service construction. We called it a “hot tap”. Once in a great while something goes wrong and all hell breaks loose.
Iron, Aluminium and Plastic will burn If it’s iron it’s called rust, it’s all oxidation.
Natural gas is a gas at normal temperatures.
It can be and is forced into a liquid under pressure. Hence LPG otherwise known as Liquefied Petroleum Gas.
Do not know if gas pipe is combustible, but when I installed my furnace I strapped the gas supply up tight to give it 1 inch cleaance from my type b vent just to be safe, assumed it was considered combustible, but I guess if i really think about it is not, was easy enough to get 1 inch clearance so I didn’t worry about it.
That looks like CSST gas pipe (e.g. TracPipe or Gastite) that consists of stainless steel corrugated tubing with a polyethylene outer jacket. That type of outer jacket has a ASTM-E84 flame spread rating of around 10 to 15, which is not very combustible, but it would still not meet typical model code requirements for a “non-combustible” material under ASTM-E136.
Accordingly typical clearances to “combustible” materials (defined by model codes like the IRC as anything that does not meet the ASTM-E136 requirements for a “non-combustible” material) would need to be provided.
JMO & 2-nickels … 
2000 IRC **SECTION R202 DEFINITIONS
****COMBUSTIBLE MATERIAL. **Any material not defined as
noncombustible.
**[FONT=Times New Roman][size=2]NONCOMBUSTIBLEMATERIAL. **Materials that pass the
test procedure for defining noncombustibility of elementary
materials set forth in ASTM E 136.
I am checking into the yellow jacket material, and its ASTM standard.
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Me?? Well, I’m not so very bright, you see. So I wouldn’t be able to concern myself with all the technical applications discussed in this thread.
Had it been I that found that CSST against the B-vent, I would have pushed it away from the contact and went on about my business.
Sometimes I think we get so wrapped up in “reporting” and “calling out” that we make out the insignificant stuff to be somewhat earth-shattering…
Everything will burn - the big question is there a problem in the pix
Answer – No – would all feel better if there was additional spacing _ YES
How one reports it is a matter of personal judgement - remember we can’t use code as our logic.
Non standard workmanship is always a good way to state an issue
rlb
Wiring inside a fuel tank in an airplane can cause a problem that will cause the airplane to shorted its flight plan
The close prox of the gas line and the vent is really not the issue – It probably will not even become an issue if some chain of event were to cause a gas line leak
BUT would all feel better in YOUR judgment if the line was moved a little
Your client is paying for your OPINION give it
rlb