Often used to cool warehouse aisles and production lines, these fans generate a stream of air that travels farther than air from conventional fans. They have a motor that is UL listed for Class I, Group D; Class II, Groups F and G hazardous environments. All fans have a totally enclosed motor enclosure, which can be used in dirty, dusty, and damp environments. Fans with wheels can be rolled into place before they are hardwired. They do not allow for movement once the unit is in use. Direct-drive fans have fewer moving parts than belt-drive fans for less maintenance.