We have a Propane
fill station at our Hardware Store, and here's some info about propane
that we've been trained to tell our customers:
Even with the new, required OPD valves , which limit the fill to 80%, there is still a relief valve on every tank. So, a full tank could still release propane
, especially if it's left in a car (or camper) on a hot day.
Always carry and store consumer type (20,30, 40lb) propane tanks upright. Another relief valve issue. Tanks on their side will put more pressure on that valve and sometimes release propane.
Per DOT reg's , up to 90lbs, or about 21 gallons, (4-20lb tanks, 3-30's, or 2-40's) can be transported inside your vehicle.
So, back to the theft issue. Empty tanks could be stored with the valve closed, inside the trailer at the storage facility.
A good idea might be to store the tanks at home, outside in the yard, or next to the house or garage, or in a vented storage building, or open shed. I use a vented plastic "deck box" to store several 20lb. grille tanks near my house.
Propane sinks, so make sure any storage "cover" or building is vented also at the bottom as well as at top for air circulation.