The cooler may be a rotating drum or a fluidised bed. Either way, cool air is brought into intimate contact with a hot – and usually granular – product which is tumbled through the cool airstream in the case of a drum or air fluidised in the case of the fluidised bed. Heat is taken out of the hot product and into the airstream which must be extracted and filtered, since it will have gained a loading of particulate matter during the process. Even if the hot product has significant moisture content, the action of heating the airstream results in driving down the relative humidity of the air, so wetting of the filter media is not to be expected. The flows are usually large, so the FabriPulse Fusion will be an expected choice.