Air King's 9166 20" whole house window fans bring fresh air in or exhausts stale air out of residential settings and are powerful enough for light commercial use. The Air King 9166 window fan features a powerful and durable motor that provides the needed amount of air movement. The fan can be set for intake or exhaust and mounts into windows 27 inches to 38 inches wide with a height of at least 26.25 inches. The special Storm Guard mounting system allows the fan to be installed in front of the window so that in bad weather the window can be closed behind the fan without having to remove it. Constructed of an impact resistant plastic housing with powder coated metal grills and blade. ETL listed and complies with OSHA requirements.