The refrigerator door has to be opened at times to put things in or take things out. When that happens, some outside air is bound to enter the refrigerator. Usually the air coming in from outside has higher humidity than the air in the inside. The mixing of the inner and outer air, therefore, leads to condensation of mois¬ture. This builds up on the cold cooling surface of the refrigerator, where it deposits as frost. This process goes on and on as the fridge is opened and shut frequently. Ultimately, one ends up with thick layers of frost in the deep freezer compartment of the refrigerator.