I recall reading warnings on other Fuel tanks that read “Caution: Contents may forcefully eject” Or ... “Open slowly” None of those tanks caps flipped up btw. Nice young man. Sorry he got hurt, I shudder to think what would’ve happened if he hadn’t made it back to his line... One time near dark, I was cutting after a break and failed to notice I had mis-threaded the fuel cap. I started it again, ran it about 10 seconds and “Whuff!” I had a fire. Incredibly scary. Saw got pitched in the pond and I lost some arm hair and got reminded of one of the best pieces of advice ... “You can never be too careful.” I never did that with a fuel cap in my lifetime... until I did.