In potentially explosive atmospheres, a distinction is made according to the frequency and duration of the occurrence of an explosive atmosphere. The correct zoning is crucial for selecting suitable components and reliably avoiding the risk of ignition.
An explosive atmosphere in zone 0 is present for longer periods of time or permanently, for example inside tanks, pipelines or reactors. That means this zone is particularly critical in terms of safety and requires materials, seals and temperature resistance of the highest standards. Only specially authorised devices and sensors that do not represent an ignition source even in the event of long-term exposure may be used here.
Areas in which explosive gases or vapours regularly occur during normal operation are classified as zone 1. This is the case, for example, in filling and emptying processes, in gas distribution or mixing systems or when transferring products between reactors and storage tanks. Devices must be designed in such a way that they do not cause ignition even if they come into frequent contact with an explosive atmosphere.
Zone 2 describes areas in which explosive gases, vapours or mists only occur briefly and irregularly, for example in the event of leaks or in the vicinity of compressors and pipe systems. Devices that work safely under normal operating conditions and do not represent a source of ignition even in the event of malfunctions are sufficient.
Zone 20 describes areas in which explosive dust atmospheres are constantly or frequently present, for example in silos or filter systems. The same strict requirements apply here as in Zone 0 for gases: all devices must be protected against dust deposits, heat development and electrostatic charging.
In Zone 21, an explosive dust atmosphere regularly occurs during normal operation, for example in filling systems, mixers or in the vicinity of discharge systems. Devices must be dust-proof and heat-resistant to prevent ignition.
Zone 22 covers areas in which explosive dust atmospheres occur only occasionally, e.g. in packaging, food or conveyor systems. Components used in this zone are reliably protected against dust and temperature increases under normal operating conditions.