本国际标准规定了确定固体生物燃料的总热值的方法 在恒定体积和参考温度25°C下，通过燃烧校准的炸弹量热仪 认证的苯甲酸。 得到的结果是所有水分析样品在恒定体积下的总热值 燃烧产物为液态水。实际上，生物燃料以恒定（大气压）的压力燃烧 并且水不被冷凝（作为蒸汽与烟道气一起去除）或冷凝。在两者之下 条件下，所用燃烧的操作热量是燃料的净热值恒定 压力。也可以使用恒定体积的净热值;给出公式计算两者 价值观

ISO 18125:2017 specifies a method for the determination of the gross calorific value of a solid biofuel at constant volume and at the reference temperature 25 °C in a bomb calorimeter calibrated by combustion of certified benzoic acid. The result obtained is the gross calorific value of the analysis sample at constant volume with all the water of the combustion products as liquid water. In practice, biofuels are burned at constant (atmospheric) pressure and the water is either not condensed (removed as vapour with the flue gases) or condensed. Under both conditions, the operative heat of combustion to be used is the net calorific value of the fuel at constant pressure. The net calorific value at constant volume may also be used; formulae are given for calculating both values. General principles and procedures for the calibrations and the biofuel experiments are presented in the main text, whereas those pertaining to the use of a particular type of calorimetric instrument are described in Annexes A to C. Annex D contains checklists for performing calibration and fuel experiments using specified types of calorimeters. Annex E gives examples to illustrate some of the calculations.