The retention bucket is a completely watertight container. It is used to collect possible spills or discharges during the storage or transfer of dangerous chemicals, thus avoiding environmental contamination. The retention capacity of a bucket must be 10% of the volume of the containers placed on it and, in any case, the volume of the largest container.

The retention bucket must be resistant to the type of spill it will contain: plastic bucket for spills of corrosive liquids; steel buckets for flammable products and stainless steel for corrosive and flammable chemicals at the same time.

The buckets can be equipped with racks, legs, lifting support for transfer, ramps and "Tray (container)" trays for holding jugs.

In October 2017, Royal Decree 656/2017, of June 23, came into force, approving the Regulation for the Storage of Chemical Products (APQ) and its Complementary Technical Instructions MIE APQ 0 to 10.[1]​ To guarantee compliance with the regulations in force, the buckets must be approved and certified.[2]​.