The K2 filter is a type of protective filter designed for respirators and half masks. This designation is based on the European standard EN 14387, which classifies filters according to the type of substances they protect against and their capacity. The letter 'K' specifies protection against ammonia and its organic derivatives, such as amines. The digit '2' indicates the filter's capacity, which in this case is medium. Medium capacity means that the filter is able to capture medium concentrations of harmful substances for a specified period, which is more than Class 1 filters but less than Class 3 filters. These filters are used in environments where the mentioned gaseous substances are present, for example, in agriculture when working with fertilizers or in the refrigeration industry.