Constant effort to reduce heating costs leads to production of not only high-quality pellets from pure wood but also cheaper vegetable pellets of inferior quality in terms of energy properties.(1,2) The combustion of alternative pellets in small boilers causes many problems, mainly ash sintering, as a result of their low melting temperature.(3,4) The paper focuses on experimental determination of bed temperatures in the burning layer during wood pellet combustion. The bed temperatures are important for prediction of combustion phases and better localization and description of sites that are critical for the sintering of ash particles as temperatures are close to the ash melting points. This experiment describes a method for measurement of the temperature field in the symmetry plane of the burner during wood pellet combustion in the retort burner. The measurement of temperature profiles at different locations in the burner shows that the combustion process in the retort burner is rather more horizontally stratified than vertically stratified. The main combustion process takes place in a ring-shaped space around combustion air inlets.