Aqueous-organic solutions can flash only over a limited composition range. This manuscript proposes a model to estimate the two critical parameters, maximum flammable content not to flash and the maximum flash point temperature, in judging whether an aqueous-organic solution is flammable or not. The results are applicable to flammability elimination and flammability hazard assessment of liquid solutions. Validation of this model was performed with measurements for 14 aqueous-organic miscible and partially miscible mixtures. Various mixtures were tested including alcohols, ketones, and esters in aqueous solutions. Overall, the estimation of the maximum flash point value and maximum flammable content not to flash were acceptable when using the proposed model. The termination of the flash for aqueous solutions was clarified to be the nonflammability of the vapor phase resulting from the high-steam concentration when the temperature of such solutions is greater than the maximum flash point. (c) 2017 American Institute of Chemical Engineers AIChE J, 63: 263-271, 2018