The knowledge of the ignition behavior of dust-air mixtures due to electrical sparks (MIE, Minimum Ignition Energy) and hot surfaces (MIT, Minimum Ignition Temperature) is important for risk assessments in chemical production plants. The ignition behavior determines the extent and hence the cost of preventive protection measures. This paper describes the use of the minimum ignition energy and minimum ignition temperature as very important safety indexes in practice. (C) 2000 Elsevier Science Ltd. All rights reserved.