In this paper, a new diagnostic tool is tested to spatially characterize combustion fluctuations. This tool based on fast infrared imaging of flames was applied on two different types of gas turbine burners and, on two traditional industrial burners varying the fluid dynamic conditions. Both gas turbine burners evidenced oscillations at low frequencies around 25 Hz, 100 Hz and at higher frequencies up to several kHz. Typical frequencies bias toward combustion were identified. The investigations also evidenced that the typical frequencies shift up while increasing Air-Fuel ratio. The technique allowed identifying these high frequencies in the 2D dimensions. The extension of the technique to a practical Lean Premixed gas turbine gave good results either for frequency analysis of fluctuations, either for the location of the phenomenon of humming. Regarding to industrial boiler combustion the technique allowed to identify on both gas and coal combustion the proper location of the flame root and to identify the best performance in term of stability. (c) 2012 Elsevier Inc. All rights reserved.