Abstract: A post treatment for cellular foam blocks such as polyurethane which includes recirculating reactant laden air through a foam block which has been slit along opposing side faces following formation. The faces are slit to a depth of one-eighth to three-eights inches with adjustably fixed knives. The slit foam block is then covered and positioned against a blower assembly in an air infiltration chamber and one side of the block is urged against air inlets whereby air is directed into the opposite face where it passes through the foam and is recirculated thereby removing the heat and finalizing the cure of the foam in a complete and consistent manner with better compression-set properties.