Interesting. I've never dealt with propane. I'm guessing the same is true for the large tanks used to supply homes outside the city utility zone,
I've got a good propane story...
Back in the early eighties I was working swing-shift as a pipefitter apprentice on a nuclear reactor construction site (in the Hanford area, Washington State). One day my foreman tells me that I'd been "volunteered" to be on the fire brigade, or fire watch, or whatever it was called, which basically meant I would have to go to a meeting every month and show up to help fight any fires that occurred (which, up to that point had never happened). Of course within a few days, and before I'd been to a single meeting, a medium size pole building that was being used as a shop for the insulators or painters was on fire and all fire brigade members were called out to fight the fire. So I mosey on out in the dark, not knowing where to go, what to do, or for that matter, any of the other people I'm supposed to be meeting with. Turns out it's not hard to find a burning building at night.
Once I got there the building was burning pretty good and there were a bunch of guys inside on a hose trying to put the thing out. Most of the people outside were yelling to get those guys out of there and I agreed completely especially since the roof had caught fire. But you'd think those guys were putting out their own house because they weren't giving up. Then, suddenly, WHOOOOOOOOOOOOSSSHHHHHH - followed by a chorus of "HOLY SHIT"! Right next to the building a column of flame shoots out of the ground at least 30 feet high and night turns to day. It turns out that there was a big propane tank buried in the ground next to the building and the pop-off valve had finally let go.
That got those guys out of the building.