Refrigeration systems in supermarkets use a variety of technologies: mechanical refrigeration, insulated holding cabinets, and air-conditioning. Mechanical refrigeration systems use fans to push cold air around the store from large refrigerators located in a centralized plant room. Insulated holding cabinets use insulation and heavy duty shelving to keep food cool. Air-conditioning uses powerful fans and coils to move heat from the indoor environment into the store, cooling customers