The replacement of fossil fuels with renewable sources for heating and drying of cereals nowadays generates a great deal of debate. The greatest representation in renewable fuel sources has biomass, particularly woodchips and straw. This paper presents the results of check measurement on a heat source for heating and warn water preparation. Selected dependences of production of carbon monoxide, carbon dioxide, nitrogen oxides, content of oxygen, of total organic carbon are presented. This knowledge implies requirements to abandon the idea of ecological harmlessness of heat production from biomass. As far as biomass substitutes fossil fuels, the environmental impact is more favourable. and Obsahuje seznam literatury