The casings are manufactured in heavy gauge galvanised sheet steel.Side panels are removable on both sides for ease of access.All models incorporate:Double inlet backward curved centrifugal impellers, helps to maintain airflow as filter pressure changes.Airtight cabinet to avoid spread of the condensates.Threaded drain connection for condensate.Inspection door on the scroll of the fan to assist cleaning.Transmission by trapezoidal drive and pulley (diameter motor pulley variable).In standard versions the transmission is located on the left, if we look from the mouth of aspiration.Transmission on the right, on request.Supplied with inlet & outlet flanges.Transmission by trapezoid belt and pulleys with gorge.Motor outside the air stream, mounted within the fan cabinet.