This section of IEC 1241-2 specifies a method of test to determine the minimum ignition energy of a dust/air mixture by an electrically generated high-voltage d.c. spark. This test method is intended to develop data to be used in deciding whether or not combustible dust/air mixtures are considered to be ignitable with respect to electrical discharge. It is intended that the dust be tested in a form (particle size, moisture content, etc.) representing conditions of actual use so that assessment of the hazard present can be made. Ignition energies determined by this method would be compared with ignition energies of other dusts to assess the relative hazard with regard to ignition by an electrical or electrostatic discharge, thereby permitting decisions to be made on the suitability of electrical apparatus for installation in areas where combustible dust is present. The test method is not suitable for use with recognized explosives, gunpowder, dynamite, explosives which do not require oxygen for combustion; pyrophoric substances, or substances or mixtures of substances which may under some circumstances behave in a similar manner. Where any doubt exists about the existence of a hazard due to explosive properties, an indication may be obtained by placing a very small quantity of the dust in question on the heated surface of the apparatus described in section 1 of the IEC 1241-2-1, heated to 400 °C. NOTE – Precautions should be taken to safeguard the health of personnel conducting the tests against the risk of fire, explosion and/or the effects, including toxic effects, of combustion. Compliance with this international standard does not itself confer immunity from legal obligations. Annex B of this section includes guidance on the significance of minimum ignition energy with respect to electrostatic discharges.