Starting with a practical drying process and an explosion case, the significance of modelling the solvent vapor concentration is discussed. With a simple calculating equation and several mathematical and experimental methods used, a model of flammable gas concentration during the drying process is proposed. Key factors that influence the concentration value most are obtained to give a method of controlling the concentration of solvent vapors in order to avoid explosion danger. Practical applications and field experiments have been made to prove the accuracy of the model and the feasibility of the concentration control method. A satisfactory modelling effect is shown in the results and a successful improvement to an actual drying process is also made by reducing the top solvent vapor concentration to 3.7%, which is below the lower explosive limit.