Industrial ventilation and heat dissipation time are important factors due to high temperature and emissivity coefficients of heat source conducive to radiation and convection produced indoors. The main aim of this study was to investigate the separate effects of four different gases (air; nitrogen, N2; carbon dioxide, CO2; and water vapor) on radiation/convection in an industrial complex with a heat source. The heat source surface is opaque or semi-transparent and two radiation models, P1 and discrete ordinate (DO), are compared in different Grashof numbers (Gr), ranging from 108 to 1011. Surface transparency has the most and the least effects on CO2 and water vapor, respectively. Water vapor has efficient natural ventilation at all heater lengths. High absorption coefficient (ap) at high Gr prevents dampening effects of radiative relative to convective parameters. The radiation model type for precise numerical simulation is indispensable with ap reduction. The opaque surface is most efficient to transfer energy only in the temperature distribution specific area, while the semi-transparent surface concentrates on temperature rise around the heater itself. The Nusselt of radiation (Nur) in P1 is more than DO model for all gases. Incident radiation for CO2 and water vapor follows a complete descending trend with progressive distance from heater, while a peak and trough trend is observed for N2 and air.