May I suggest a slightly different vulnerability?
Old fashoned lead solder 'til it was withdrawn for all but aerospace and other critical applications has a very low melting point.
Plumbing joints (copper pipe, lead solder ) occasionally fail - particularly near vibration (if the pipe passes behind a washing machine, so much the better), or hot/cold thermal cycling (by a radiator, in the sun etc.).
Turning the gas off, a pipe-joint may be heated with a heat-gun, these can produce temperatures up to 400 Celsius (750 F) - way hotter than the 183 C (631 F) lead solder needs.
If you want to go small and portable heat guns come pocket sized:
As the solder drips out of the joint, collect some of it, let the rest drop to the floor - the less solder the crime scene guys find after the explosion and fire, the more chance they'll believe the plumber shorted the joint doing a piss poor job. Make sure to stop before the joint falls apart totally.
Turn the gas back on again, set your candle in the next room or whatever you plan and quietly get out of there. The explosion and fire will easily be hot enough to melt all the remaining solder in the pipe joints and hide any scorch marks you may have left.