I leave it on all the time for the frig.
When fueling, the gas filler door is about 20 feet behind the frig, and the frig is about 5 feet off the ground. Gas fumes are heavier than air. If the fume level is that deep, when I start the engine, the sparks from the cranking motor commutator/brushes will ignite them, and there will be a huge fireball.
I have never heard of that happening.
Yes, there was (is?) a video making the rounds showing a Class B going up in flames when the owner was beginning to fuel it, because (supposedly) the frig was operating on propane. There are two things to notice about that video:
1. The frig was about a foot above the fuel filler.
2. The gas nozzle was locked OPEN, and the owner sprayed fuel directly into the frig!
That was a one-time freak occurrence, yet it has become the "poster child" for the "We're all gonna DIE if you don't fuel up properly!" folks.
Fuel station explosions are really VERY rare!
CM1, USN (RET)
2017 Jayco TT
Daily Driver: '14 Subaru Outback
1998 Dodge QC LWB, Cummins, 5 speed, 4X2
2 Kawasaki Brute Force 750 ATVs.
Pride Raptor 3 wheeled off-road capable mobility scooter
"When seconds count, help is only minutes away!"