Drums in transit rub against each other and sometimes wear through or split. Drums in long-term storage often corrode with resultant leakage.
Leaks can result in the risk of exposure to workers and the public.
There is also the risk of incompatible substances mixing, with subsequent reactions such as fires and explosions. A pallet made of, or coated with, chemical resistant plastic that forms a sump under the drums and would thus contain any leakage. The sump holds the entire contents of a 200 litre drum. Plastic pallets are rot and corrosion resistant. In addition the risk of incompatible dangerous goods being mixed is also reduced.