To investigate the thermal environment and pollutant distribution in industrial plants with large-area pollution sources

on-site measurements were conducted in a naturally ventilated graphitization workshop. During different cooling stages

the surface temperature of pollution sources

indoor thermal parameters

and concentrations of SO2 and particulate matter (PM2.5 and PM10) were recorded. In addition

the micro-morphology

elemental composition

and particle size distribution of the collected particulates were analyzed. The field test results indicate that the cooling process can be divided into three stages: the initial

middle

and final stages. During these stages

radiative heat dissipation accounts for 49.4 % to 60.0 % of the total heat loss. The current natural ventilation rate is 25.3 % lower than the theoretical requirement

and the wet-bulb globe temperature (WBGT) at the post ranges from 25 °C to 32 °C. The results of the Kruskal-Wallis test indicate that the differences between parameters at different cooling stages are statistically significant. In the initial cooling stage near the source

the concentrations of SO2 and PM2.5 are 0.95 to 2.68 times and 2.1 to 3.5 times higher

respectively

compared to the middle and final stages. During the testing period

the ratio of PM2.5 to PM10 ranges from 12.72 % to 62.52 %. A positive correlation is observed between the thermal environment parameters of the factory and pollutant concentrations

with the strongest correlation occurring in the early cooling stage. The correlation coefficients between air temperature and SO2

PM2.5

and PM10 are 0.67

0.59

and 0.51

respectively. Laboratory analysis reveals that the particles exhibit irregular shapes

such as block-like and flake-like forms. The cumulative particle size distribution follows the Rosin-Rammler distribution

with a characteristic size of 53.618 µm. This study provides valuable references for CFD simulation parameter settings and ventilation system optimization in the indoor environment control of factories with large surface pollution sources.