I had 600 gallons of propane delivered one day last week. A couple days later I smell gas. Yep, the tank was leaking. It was a big brew-ha-ha with the gas company coming out; told me to call 911 (waited about an hour for the repairman, then did call the sheriff) Nothing happened, except I lost who knows how much propane at $1.79 a gallon. Oh, did I mention this was all happening around 1 a.m. I guess these yellow crystals must be the propane??????