MIE experiments and simultaneous measurement of the transferred charge – A verification of the ignition threshold limits

Using the apparatus for the determination of the MIE a wide series of experiments have been carried out in hydrogen/air, ethene/air, propane/air and acetone/air mixtures. The transferred charge as a criterion to judge the ignition potential is determined to verify the thresholds of transferred charge given in the standards. The stored charge in the capacitance before the discharge is compared to the transferred charge in the spark. The correlation of ignition energy and transferred charge is examined and the thresholds of the transferred charge are discussed. The MIE of the above-mentioned mixtures are reviewed taking into account the measurement uncertainty.

► The current transferred charge thresholds represent different levels of safety.
► The MIE value of propane/air could not be verified.
► The MIE of acetone/air is found to be lower than the value given in literature.
► The expanded measurement uncertainty concerning MIE values can be as much as 10%.