The bolt together FRP casing is completely non-corrosive. The casing enclosing the PVC fills services to isolate the air stream, which passes over the fills. The casing is bottle shaped to reduce frictional resistance of air and aid air flow pattern. It is designed to withstand wind loads upto 75km/hr, and vibrations emanating from the motor and other equipment. FRP casing has a high impact resistance when laminated with Isopthalic Resin and even if damaged, is easily repaired at site. The Neopently Glycol gel coat is U.V. inhibited to provide a long lasting finished appearance and service life and imported wax release agents helps retain colours for long periods even when exposed to direct sunlight. The casing is in sections of easy to handle sizes and is assembled at site using bolting joints. The bottle shape of casing is ideal with regard to cooling efficiency and space economy.