Keeping things cold in the RV refrigerator while traveling?

I've worked in a number of manufacturing environments where we deal with thousands of gallons of flammable materials. The general rule of thumb is that in open areas, ignition will only occur within 3' of the ground as the vapors of flammable liquids will very rarely be able to reach explosive levels above that height. They are heavier than air, and stay low and dissipate.