This paper describes the methodology that aims at detecting tube temperatures and diagnosis of heating medium in presence of visible and invisible flames, by means of sequences of the narrowband images stored during steady position of the applied camera. The main special feature of elaborated techniques is the dynamic spectrally matched IR thermography, which bases on forming single images that consist of pixels of chosen statistical value, minimum and maximum, noted during adequately long sequence of thermograms with total independence to the moment of their capture. Arrays of these data can be used directly, or as inputs to other artificial images. In this way, additive or suppressed interferences of fluctuating character could be minimalized or exhibited, depending on the type of investigations. By the use of properly chosen optical filters and algorithm, the elaborated method offers a new possibilities to test temperature problems other than more reliable tube temperature measurements, as for example study of heating medium features, symmetry, etc.