ISO 589:2008描述了测定硬煤总含水量的两种方法，即两阶段法和单阶段法。对于这两种方法，可以选择在空气中干燥或在氮气气氛中干燥。根据煤的等级，通过在不同大气中对样品的子样品进行干燥而获得的结果可能存在系统性差异。在氮气气氛中干燥适用于所有硬煤，而在空气中干燥仅适用于不易氧化的硬煤。

ISO 589:2008 describes two methods for determination of the total moisture content of hard coals, a two-stage method and a single-stage method. For either method there is a choice between drying in air and drying in a nitrogen atmosphere. Depending on the coal rank, there may be systematic differences between the results obtained by drying in the different atmospheres on subsamples of a sample. Drying in a nitrogen atmosphere is suitable for all hard coals, while drying in air is only suitable for hard coals not susceptible to oxidation.