Fiberglass & poly wall exhaust fans are the right choice for horticulture, agriculture, indoor pools buildings, or anywhere corrosive and caustic chemicals may be present in the atmosphere.  These wall ventilation fans come in belt drive and direct drive versions.  Included shutters are mounted to be on the interior, instead of the typical shutter mounted ventilator fan, whose shutter is on the exterior of the building.  For areas where flammable fumes or gases may be present an explosion proof version of these fans are available.