An experimental investigation of laminar, transitional and turbulent free convection in air is described. Data of temperature field for modified Rayleigh number lower than 2.7×(10)^<14> and heat generation between 30.5 and 335.8W/m^2 includes percentage heat flux distributions by radiation, local heat transfer coefficient distributions, mean temperature profiles in boundary layer and correlation of temperature fluctuations between wall temperature and in boundary layer. Results are compared with other theoretical and experimental data. Local heat transfer coefficient distribution for turbulent boundary layer is similar to Cheesewright's result.