This International Standard establishes a classification of brown coals and lignites by types on the basis of total moisture content and tar yield. Until reliable parameters for differentiation of brown and hard coals are worked out and confirmed, coals considered in each country as brown, on the basis of a number of other characteristics, should be classified as brown coals regardless of their calorific value, i.e. including the cases when the gross calorific value of the coal in equilibrium with air at 30 °C and 96 % relative humidity is more than 24 000 kJ/kg on the ash-free basis.