An electronic equipment enclosure includes a frame structure at least partially enclosed by a plurality of panels defining a compartment in which one or more electronic components are mounted and an exhaust air duct that is adapted to segregate hot air being exhausted from the compartment from cool air entering the compartment, thereby improving thermal management of the enclosure. The exhaust duct includes a lower duct section extending upward from the top panel of the compartment and an upper duct section telescoping upward from an upper end of the lower duct section. Each duct section includes four panels connected together by hinged corner fittings such that the section is collapsible. The upper duct section includes an outwardly flared portion.