Hi folks. I've had time to Google around and I think I have found the answer to my question. Simply put, yes, I can switch on my Streamlight Propolymer and be confident that I won't blow myself up in the presence of a gas leak after an earthquake.

I found a nice description of these Class and Division categories here Defining Class I specifications and subgroups

If you're looking for a light that is safe around natural gas leaks, looks like you want a flashlight that is approved for Class I, Division 1, Group C, D which is exactly what the Streamlight Proplymer series is approved for.

Like I said in the parent, it's a great general purpose flashlight.