I've had a couple one gallon jugs fermenting get clogged with krausen, blow the stopper and spray the ceiling. Just one gallon of beer. I was never home when it happened either time but I'm sure it was loud and terrifying for my cats.
Those were the early, barely temperature controlled days where I put the jugs in plastic storage bins of water in my Texas apartment which did little to stop them from fermenting into the 70s. That was the end of not using blowoff tubes with those jugs.