The thesis deals with the issue of explosion of food powders and flours. The aim of this diploma thesis is to determination of lower explosion limit, bulk density and thickness of the dangerous layer of selected food powders: wheat flour, light brown wheat flour, wheat flour, wheat flour, coarse wheat flour, wheat dust, wheat barley, wheat grinding passage, wheat bran, rye flour, rye powder. To achieve the objective of the work I followed the methodology of this thesis. An explosion chamber VK100 was used for the experimental determination of the lower explosion limit. The sieving was carried out on a RETCH AS200 sieve machine and the results of the lower explosion limit and bulk density were used to determine the thickness of the hazardous dust layer. The lower explosion limit is the lowest explosive concentration of explosive air / combustible dust mixture. Once the experiments are completed, we can confirm that wheat flour is the most risky raw material. The lower explosive limit of flour was the lowest, 28 g/m3 and the dangerous layer thickness was the smallest 0.29 mm and the percentage of particles smaller than 250 µm was 86.7 %. Wheat flour is the safest processed raw material in the mill compared to all other samples. The lower explosion limit is 100 g/m3, the dangerous layer thickness is 0.69 mm and the percentage of particles smaller than 250 µm was only 1 %. The biggest danger of explosion is in the production of light wheat flour. All samples examined may cause an explosion or fire and therefore it is important to take precautionary measures in the form of fire and explosion protection by organizational and technical security.