gas pipe

Hi all.

I've got a 4 1/2' crawl space under the house, which I'll be running the gas and ch pipes. Handily someone has knocked a hole through the load bearing wall, , (need to get some mini acros or timber under there...), so I have access from front to back. I have an open fire above the route I'd like to take, so how far away should I put the gas pipe? I'm putting plasterboard/ insulation in and the pipes will be hung underneath/ on the wall, for ease of access.