If the occurrence of a dangerous, potentially explosive atmosphere cannot be reliably prevented, further explosion protection measures are required. These include the classification of the potentially explosive atmosphere into explosion protection zones in accordance with the criteria of probability and possible duration of the occurrence of a potentially explosive atmosphere. Based on the zone classification, only approved components may be used in these areas in order to eliminate sources of ignition. This leads to the prevention of ignition of an existing, potentially explosive atmosphere, which is designated as secondary explosion protection.
Structural explosion protection, which reduces the effects of a potential explosion to an acceptable level, is designated as tertiary explosion protection. This includes, for example, pressure-resistant construction or the securing of the plant against explosive pressure with safety features such as explosion vent panels and valves.