The issue is pressure relief when inside the car....
Given most re-fill places don't fill using the correct procedure......nearly every time they let go of the full line and nip the bleed screw up while liquid is still coming out....as temperature changes I.e. Increases the cylinder let's out vapor, liquid in done cases.
I reckon most explosions happen when the cylinder has been left in the car after refill and there has been a temperature change.....gas is at a floor level, person drives off and at some stage it ignites, oh and cylinder is secure upright I.e. Rolling around
Get a cylinders filled than straight into a car with either air-con on or windows will probably be cooler than when filled. Oh and secured upright.
Remember gas is heavier than air so even with with windows down gas can still linger in the foot wells.
