Olfactory navigation requires comparing of, odor concentration across samples distributed in space and time. One potential strategy of odor source localization is sequential (temporal) comparison: the animal chooses direction in the olfactory surroundings by detecting concentration changes in time (ΔCt) across consecutive inhalations. To study the neural processing of ΔCt, we developed an odor delivery system that allows rapid switching and stabilization of different concentrations of an odor, such that concentration can be changed on each sniff. We monitored activity of mitral/tufted (M/T) cells in the olfactory bulb of mice in response to prolonged concentration presentations and to stimuli that flicker between concentrations from sniff to sniff. We find that a subset of M/T responses are sensitive to ΔCt, responding primarily to concentration changes. Our results indicate that M/T cells explicitly compute ΔCt, providing a signal that may guide navigational decisions in downstream olfactory circuits.