This document specifies a test method for the quantitative determination of ignition delay of middle distillate fuels intended for use in compression ignition engines. The method utilizes a constant volume combustion chamber designed for operation by compression ignition, and employing direct injection of fuel into compressed air that is controlled to a specified pressure and temperature. An equation is given to calculate the derived cetane number (DCN) from the ignition delay measurement. This document covers the ignition delay range from 2,58 ms to 6,34 ms (76,8 DCN to 33,9 DCN). The combustion analyser can measure shorter or longer ignition delays, but precision is not known. This document is applicable to diesel fuels, including those containing fatty acid methyl esters (FAME) up to 30 % (V/V). The method is also applicable to middle distillate fuels of non-petroleum origin, oil-sands based fuels, blends of fuel containing biodiesel material, diesel fuel oils containing cetane number improver additives and low-sulfur diesel fuel oils. However, users applying this standard especially to unconventional distillate fuels are warned that the relationship between derived cetane number and combustion behaviour in real engines is not yet fully understood. The test method is also applicable to the quantitative determination of the ignition characteristics of FAME, especially the ignition delay. However the correlation data available were inconclusive about the precision of the equation. So the determination of derived cetane number for FAME fuel, also known as B100, has not been included in the precision determination as in Clause 12. An interlaboratory study executed by CEN in 2013 [1] confirmed that this test method is also applicable to paraffinic diesel from synthesis or hydrotreatment, containing up to a volume fraction of 7 % fatty acid methyl ester (FAME) and that the precision by this test method is comparable to conventional fuels. NOTE 1 On 13 July 2021 ASTM International has granted usage of its national Diesel Exchange group program data based on which the lower end of the ignition delay scope has been expanded from 2,8 ms up to 2,58 ms (from 71 DCN up to 76,8 DCN). The relevant subcommittee ASTM D02.01 has not endorsed this scope expansion and therefor did not adopt the conclusions for its equivalent standard [3]. Supporting data have been filed at CEN/TC 19 Secretariat. NOTE 2 For the purpose of this document, the expression % (V/V) is used to represent the volume fraction and % (m/m) the mass fraction. WARNING The use of this standard may involve hazardous materials, operations and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.