Locker system for delivery of heat sensitive products

A locker system for delivering heat sensitive products, the locker system comprising:

• a plurality of lockable compartments including at least one refrigerated lockable compartment, a control unit for controlling said plurality of lockable compartments, a cooling device comprising an expansion chamber receiving liquid CO2 from a reserve of liquid CO2 and delivering gaseous CO2 in each of said refrigerated lockable compartments through at least one common duct, and an extraction system to avoid concentration of CO2 in a building where the locker system is located, wherein the expansion chamber comprises a combination of valves and optionally a pressure sensor for regulating the pressure in the expansion chamber between atmosphere pressure and an upper limit pressure, in order to maintain the internal temperature of the expansion chamber within a predetermined temperature range, and wherein the expansion chamber is divided in first and second sections by a grid, liquid CO2 being injected in the first section, the second section comprising the plurality of valves and the optional pressure sensor, openings in the grid being small enough to block solid CO2 particles, but large enough to let gaseous CO2 flow through.