Beer ferments a lot. If the beer ferments in the fermentation room, it is formed so called blanket. It is the foam, where all the dangerous substances, influenced on the beer quality are accumulated. The period of draught beer fermentation makes 7 days and in the case of special beer it makes from 7 till 14 days. The maximum temperature of fermenting beer is 11°C. After fermenting the beer is being cooled and the yeast, deposited on the bottom is being accumulated.