A method of detecting a change in occupancy status of a fluidizable bed (10) includes determining (102) an unloaded plenum pressure value corresponding to the absence of a load on the bed, determining (104) a loaded plenum pressure value corresponding to the presence of an occupant on the bed, and establishing a reference (PREF) as a function of at least one of the unloaded plenum pressure value and the loaded plenum pressure value. A signal (116, 120) is issued in response to a relationship between the reference and a value (PMON) representative of actual pressure in the plenum. The bed also includes a pressure sensor (60) for monitoring a pressure value representative of pressure in the plenum and a controller (50) for issuing a signal (116, 120) responsive to a relationship between the monitored value and a reference value.
