Abstract: The cooling system supplements the cooling of a walk-in cooler by injecting outside cold air via an outside air intake. The system includes air intake ductwork adapted to vent cold outside air into the walk-in cooler and air return ductwork that circulates the air to provide cross-flow of the injected cold air. Inline fans are connected to an interior thermostat. Motorized dampers are connected to a thermostat with an exterior temperature probe. The system thermostats are set slightly cooler than any pre-existing thermostat operating the pre-existing refrigeration system.