In sparged reactors, interfacial phenomena can produce very energetic liquid-phase motions; the important interfacial events may include bubble formation, bubble breakage and coalescence, and bubble disengagement. The latter has generally been singled out as a leading cause of cellular damage and death in the large-scale culture of mammalian cells. In the present work, the danger to cells posed by disengagement phenomena in airlift reactors is quantified through the combination of three separate factors : I) the number of exposures per hour of operation; 2) the mean residence time (per exposure) in the region of the disengagement disturbances; and 3) the disturbance energy contained in the appropriate range of frequencies. A system for estimating hazard levels in aerated reactors (based upon these three factors) is proposed. The methodology described in this paper makes quantitative comparison of both reactors and reactor operations possible.