Abstract: The invention relates to the handling of particulate materials such as foundry molding sand requiring cooling. The operating vessel has an inlet, through which material is charged to flow-downwardly in the vessel against an upward flow of pressurized fluid, usually air, there being provided sensing and signalling probes to sense the height of the fluidized material in the vessel at a pedetermined maximum level in the vessel and at a predetermined minimum level. These sensing and signalling probes control the outlet of cooled sand from the bottom of the vessel, stopping it when the minimum level is sensed and re-commencing discharge when the maximum level is reached.