what's it going to do? Start a fire in the fireplace?
It takes a fuel/air mixture to burn. There is only the fuel component in the pipe and no air so now danger of fire. I've seen the gas company guys heat an old metal gas line to red hot with a rosebud and fold it over to cap it off when abandoning it to be replaced with a new plastic line.
Gas is not as dangerous as some think. Has to have just the right conditions to burn.
I've worked the system live many times to avoid needing to relight all the pilots. It's only about a half pound pressure, you can stop it off with your finger.
Dana

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"Political Correctness is a doctrine, fostered by a delusional, liberal minority and rabidly promoted by an mainstream media,which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."