In this work, spatial-spectral experimental issues affecting the detection of radical emissions in a natural gas flame are discussed and studied by a radiometric analysis of the flame spectral emission. As results of this analysis, Local and Global Spectral Radiation Measurements (LSRM and GSRM respectively) techniques are proposed, and guidelines for selecting the radical emission bands and spatial location of photodetectors are given. Two types of experiments have been performed in order to demonstrate the reliability of the GSRM technique for combustion characterization. In the first experiment, the LSRM and the GSRM have been implemented by using a home made sensor array, based on silicon photodiodes, for sensing the excited CH* and C*(2) radicals in a natural gas flame. It has been experimentally demonstrated that by using the GSRM, the signal's dispersion can be reduced to about 86% for the CH* and 76% for the C*(2) with respect to the obtained values with LSRM methodology. In the second experiment, the GSRM technique has been applied for sensing the CH* and C*(2) radicals, where it has been found that the signals emissions ratio C*(2)/CH* provides a good indicator of the thermal combustion efficiency and the CO pollutants emissions, with small dispersion. Thus, the GSRM technique has corroborated the usefulness of that ratio for combustion monitoring. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.