Abstract: A heat operated refrigerator having a gas burner and a flue pipe, a fresh air intake conduit and a combustion gas conduit connected to the flue pipe, with the gas burner, flue pipe, and conduits forming a sealed combustion system that is separated from the space to be cooled. The fresh air intake conduit and the combustion gas conduit are so constructed and arranged to pass through a wall or roof whereby upon movements of the air about the ends of the conduits adjacent to the atmosphere a higher static pressure prevails in the opening of the fresh air conduit than in the opening of the combustion gas conduit. Thus, the ambient air variations in pressure do not affect the air flow through the sealed combustion system to such an extent that the burner flame is extinguished.