The engineering design of industrial chimneys requires predicting the temperature decay of exhaust gases along the walls of chimney. This paper investigates the practical calculation of the thermal performance of industrial chimneys which leads to estimating the static draft and the bulk temperature of combustion gases at the chimney's exit for determining the air pollution levels in the vicinity of the stack. A modified analytical model is used to obtain accurate heat transfer results. Heat transfer processes involving the internal convection heat transfer, external heat transfer to the surrounding and conduction heat transfer, which takes into account fouling resistance are considered. The present modified analytical model provides a good estimation of the bulk temperature and the outside wall temperature compared with that computed using1-D lumped model (Cortes model). The present modified model is validated with published theoretical and experimental data. The validation shows that the present modified model is more accurate than 1-D lumped model (Cortes model). The paper describes the thermal calculation procedures of industrial chimneys using the standard heat transfer correlations. The calculation procedures are easy to apply by design engineers in the field of thermal design of chimneys. Also, comparison between the present modified model and the previous 1-D lumped model with recent experimental data measured at the glass furnace chimney at El-Araby for Lighting Technology (glass factory) is discussed.