AbstractThe NO2 sorption capacity and rate of calcareous soils, a calcic soil, and a granular limestone were measured at room temperature by passing air or nitrogen gas containing NO2 through them. In dry air (humidity < 5%), NO2 sorption reached an equilibrium value within 2.5 min. In moist air (humidity > 95%), NO2 sorption increased to as much as 10‐fold that in dry air and approximately equaled the acid‐titratable basicity of calcareous soils. The sorption rate was proportional to the unreacted fraction of the capacity with sorption rate constants ranging from 0.015 to 0.03 min‐1 at a NO2 concentration of 0.5% volume. At a concentration of 0.1%, the sorption rate was slower but the capacity remained unchanged. Sorption of NO2 was similar when either air or a nitrogen carrier was used.