Abstract: A refrigeration apparatus comprises a primary refrigeration circuit of the vapour compression type. Cooling is then provided at desired locations remote from the primary circuit using a secondary circuit containing carbon dioxide as a volatile secondary heat transfer substance. The carbon dioxide is liquified in secondary condenser (cooled by primary evaporator) and is circulated by circulation pump to expansion valves and cooling units at desired locations where it evaporates and provides cooling. The volume of possibly environmentally harmful refrigerant employed in the vapour compression primary circuit is minimized.