The effects of the attenuation of the radiation by the decomposition products in the gas phase on surface temperatures of PMMA and red oak were studied by using a CO2laser in the radiant flux range from 7 to 18 W/cm2irradiating normally downward to the horizontally mounted sample. It was observed that the attenuation of the radiation caused by the decomposition products in the gas phase was significant enough to affect surface temperature. Maximum surface temperature of PMMA rises to about 400°C during the pre-ignition heating period and tends to be independent of the initial radiant flux. Surface temperature at ignition is in the range of 375 to 410°C and remains fairly constant from 8 to 19 W/cm2for piloted-ignition and auto-ignition. However, the maximum surface temperature of red oak during the preignition heating period tends to increase with the decrease in the initial radiant flux. Surface temperature at ignition increases from 400°C at 16 W/cm3 to 575°C at 8 W/cm2for auto-ignition and from 420°C at 15 W/cm28 to 500°C at 7 W/cm2 for piloted-ignition.