AbstractUpper respiratory tract irritation of male Swiss OF1mice by airborne chemicals is well correlated by the following equations for the toxicity of nonreactive compounds,FRD′50is the concentration in mol 1−1of the airborne chemical required to elicit a 50% decrease in respiratory rate, and the explanatory variables are δ2a polarisability correction term, π 2*the solute dipolarity, α 2Hthe solute hydrogen‐bond acidity, Vxthe characteristic volume, and L16the gas/hexadecane partition coefficient. These equations considerably resemble corresponding equations for gas/liquid partition coefficients into organic bases such as tricresylphosphate, but do not resemble an equation for gas/water partition