Ann: Quarterly Activities Report, page-87

Would it be fair to say, industry standards for commercial kitchens require copper to carry lpg from the lead in, manifolds etc. not 100% sure but could you clarify copper is the same for fire understanding gal is in use.
Crimping is the way to go, however most connectors on poly if not all are copper with a copper compression ring as you would be aware.
Electrical wise nothing is more conductive than copper except super conductors and gold however cost/weight is the killer for all 3. Hence aluminium underground, which kinda sux. Some sparkies among st us may agree with technology and comfort a heavier draw is required, hence gauges are typically larger with draw and length of runs.
All air conditioning lines are copper.
Aluminium is replacing copper however if the line is severed it cannot be simply re-connected as copper can be, it is a whole new pull from my understanding when dealing with hv