The diploma thesis deals with combustible and explosive dust - air mixtures of food dusts and determination of their selected fire - technical characteristics. The aim is to experimentally determine the lower explosive limit of food powder samples consisting of smooth flour, powdered sugar and cocoa using the VK 100 explosion chamber and the calorific value measurement using the IKA C5000 calorimeter according to the methodology given in STN ISO 1928. After the experiments we concluded that Examined samples of food dust are explosive and pose a high risk. The test sample of cocoa showed the most reactive, with the lowest lower explosive limit and the highest calorific value. Combustion heat values contribute to the spread of fire, so it is necessary to provide operations for the processing and production of these foodstuffs with the components of the explosion protection.