The purpose built air blast system is designed for easy defrosting and hot gas or water, or a combination of both. Air circulation is by axial flow fans fitted with peripheral electric heaters to prevent ice formation between the blade trips and the casing when the fans are not in operation. The air cooling coils are manufactured from either stainless steel or copper, both with aluminium fins, or from galvanised steel, to suit application requirements. Varying fin spacing through the evaporator ensures maximum operating times between defrost cycles. The whole of the spiral freezer system is enclosed in an insulated enclosure consisting of prefabricated foamed polyurethane panels. The floor is specially constructed in the form of a tank which is sloped to drain. The floor can be flooded during cleaning without any danger of water seeping through the waterproof tank. An under floor heating mat is supplied to prevent frost formation.