I don't know much on gas fireplaces, but if it works the same way as gas lines being ran for outside gas grills and/or pool gas heaters, which it should be, all you have to worry about is the size of the line that you need run (diameter) which is different depending on the amount of the unit your going to run gas asks for (read the instructions specs sheets on the gas fireplace you want, and it should tell you) I'm pretty sure you can always go bigger on the pipe and then reduce to the size necessary(but the bigger the pipe, the more expensive of course). My second suggestion is if you do run a line for the gas fireplace, you might as well run the line for the outside gas grill! That way you don't have to keep refilling propane tanks if that's the kind of outside grill you have. Hope this helps