VOCs are the main source of indoor environmental pollution. Bodalal established a mathematical model of VOCs emission characteristics, which provided a reference for many scholars to study the diffusion of VOCs. However, there are some logical errors in the process of mathematical derivation, which make the model difficult to understand. In the paper, first, the reasons for the error of model derivation are pointed out in detail. Second, using Laplace–Carson transform and generalised Heaviside theorem, the correct derivation process is given. Finally, a simple method for calculating the diffusion coefficient is presented and its application is given. This paper provides convenience for people to use this model in related research.