ISO 18125:2017规定了在25°C参考温度下，在通过燃烧认证苯甲酸校准的弹式热量计中，在恒定体积下测定固体生物燃料总热值的方法。 所得结果为分析样品在恒定体积下的总热值，燃烧产物中的所有水均为液态水。实际上，生物燃料是在恒定（大气压）压力下燃烧的，水不是凝结（与烟气一起以蒸汽形式排出）就是凝结。在这两种情况下，使用的有效燃烧热是恒定压力下燃料的净热值。也可以使用恒定体积下的净热值；给出了计算这两个值的公式。 校准和生物燃料实验的一般原则和程序见正文，而与使用特定类型量热仪有关的原则和程序见附录a至C。 附录D包含使用指定类型的热量计进行校准和燃料试验的检查表。附录E给出了一些例子来说明一些计算。

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.