Back in the '90s in Hell's Kitchen there was a storefront used by food cart vendors from the area to store many 20 lb propane tanks...there was a Fire in the store & as 9th BN Units & R*1 were opening up a tank or tanks let go.......could have been much worse ......(there was a video of it back then) ,,,,,,afterwards the resulting crackdown had some vendors storing several of their tanks in a small rolling trash dumpster chained shut & then chained to a store rolldown. (some complete with garbage inside )....after this was discovered & cracked down on some of the vendors simply put their tank in a black plastic garbage bag & carried it back & forth to & from their residence ....on the Subway. ..........under the right conditions a 20 lb propane tank is a BOMB.