Heat and mass transfer by natural convection in a square cavity with turbulent flow has been analyzed, covering a wide range of Rayleigh number of 10(4) <= Ra <= 10(10) with a constant value of C-H = 3000 ppm. A contaminant point source (CO2) is considered in five different positions inside the cavity. Governing equations of mass, energy and concentration were solved by the finite volume method, and a k-epsilon turbulence model was used for the treatment of high Rayleigh numbers. From the results, it was observed that contaminant point sources located near bottom wall decrease indoor temperatures, whereas point sources situated near upper wall decrease contaminant concentration levels. In general, temperatures and contaminant concentrations decrease as the Rayleigh number increases. Additionally, it was observed how the Nusselt number is directly affected by the contaminant source location. (C) 2014 Elsevier Ltd. All rights reserved.