An exhaust air removal system and method for use with a rack or enclosure containing equipment is provided. The system and method are configured for removal of exhaust air vented from equipment during operation to thereby remove heat from the equipment. In one aspect, the system includes a fan unit preferably configured to serve as a back door of an equipment rack or enclosure and configured to provide access to an interior of the rack or enclosure. The fan unit provides multiple fans coupled to internal exhaust ducts that are arranged to draw and to remove exhaust air vented from rack-mounted equipment. The fan unit is further configured to vent exhaust air to an area external to a rack or enclosure, such as an external exhaust duct or plenum. Removal of hot and warm exhaust air vented from rack-mounted equipment enables the equipment to operate effectively, drawing sufficient amounts of cooling air to meet its cooling requirements. The fan unit is constructed for portability and for easy attachment to and removal from a rack or enclosure, providing flexibility in handling equipment exhaust needs.