Had the same thing happen when I had two 30# tanks filled in the morning before headed to Myrtle Beach on a hot day. We set up camp, went up to check out the beach for a few minutes and came back to one of the tanks venting. This was before OPD so after moving the tank about 40' from the trailer opened up the valve for a minute to relieve the pressure. After hind sight, I was very lucky that the released gas dissappated before hitting an ignition source because the area I used was a bit of a bowl surrounded by campers with little wind. Got real nevous as I saw the cloud just hang around for a few minutes before it began to clear. Think the thing that saved me was it was still early in the season so not tons of folks around combined with mid morning so not a lot of folks coming or going.
Made it a point if I wasn't pulling LP from the tank, to get them filled in the afternoon when the temp was the highest. Never had the problem again with those tanks or others.
