A rack mount assembly measurement tool, for determining physical values including air flow and heat loads, includes a front assembly and a rear duct assembly that are non-intrusively and releasably mounted on the front and rear of such rack mount enclosure. Physical values are sensed at multiple vertical locations to enable a determination of overall and localized heat loads within the enclosure. Front sensor values are collected and wirelessly transmitted from the front assembly to a receiver/processor supported on the rear duct, which generates computed values that are displayed in addition to the sensed values.