In today's clean room air-handling configurations, severe physical restrictions exist that will adversely affect inlet and outlet conditions of fan operation. Fans of varying efficiencies exist among manufacturers as well as within a manufacturer's product line. Many fans are selected solely on this efficiency without consideration for system efficiency, where all elements of the system are considered and evaluated against the system performance criteria. Discusses fan efficiency vs. system efficiency, comparing a highly efficient vane fan to a relatively less efficient plug fan, noting how in some applications the less efficient fan will result in higher system efficiency in achieving system performance criteria.

KEYWORDS: fans, efficiency, clean rooms, air handling units, operations, performance, comparing, axial flow fans, vanes, centrifugal flow fans.