A new hypothesis for the understanding of chemical disinfection, which we have termed the Intrinsic Quenching hypothesis, is presented. This mechanistic treatment of disinfection kinetics is based on the hypothesis that the biocide concentration may not be in vast excess over the microbes, as is normally assumed. A mathematical model was developed and found to be useful in describing the observed kinetics of several disinfectants. The model suggested that the reason for the observation of non-linear, log-survivor curves was due to the ability of the microbes, in clean, soil-free conditions, to intrinsically quench the bulk concentration of biocide.