{"id":12515,"date":"2022-04-14T17:41:00","date_gmt":"2022-04-14T15:41:00","guid":{"rendered":"https:\/\/b3v39j.myrdbx.io\/ul-wissen\/ul-blog\/what-types-of-ex-zones-are-there\/"},"modified":"2026-07-31T18:53:59","modified_gmt":"2026-07-31T16:53:59","slug":"what-types-of-ex-zones-are-there","status":"publish","type":"blog","link":"https:\/\/krayer.de\/en\/ul-wissen\/ul-blog\/what-types-of-ex-zones-are-there\/","title":{"rendered":"What types of Ex zones are there?"},"content":{"rendered":"\n

In many industries, there are areas where there is a risk of explosion. These so-called Ex zones<\/strong> occur where flammable gases, vapors, or dusts accumulate in the air, and they impose special requirements on the planning, design, and selection of equipment. A key foundation for this is the zone classification in explosion protection<\/strong>. It defines where and how frequently an explosive atmosphere may occur\u2014and what technical measures are required. <\/p>\n\n

This article provides an overview of Ex zones<\/strong> according to European and international regulations and explains what matters in practice.<\/p>\n\n

Ex-Zones: Definition<\/h2>\n\n

An “Ex” zone<\/strong> refers to an area where an explosive atmosphere may form due to gases, vapors, mists, or dust. The classification is based on the frequency and duration of the occurrence<\/strong> of this atmosphere. <\/p>\n\n

What is an “ex-zone”?<\/h3>\n\n

“Ex zones” are therefore specifically designated areas where<\/strong> there is a risk of an explosion or dust explosion,<\/strong> since flammable concentrations of combustible gases, vapors, mists, or dusts may occur there. Depending on the hazard situation, a distinction is made between different Ex zones. <\/p>\n\n

Zone Classification in Explosion Protection<\/h2>\n\n

The zoning system in explosion protection<\/a> is used to systematically assess areas with a potential risk of explosion. The key factor is how frequently<\/strong> and for how long<\/strong> an explosive atmosphere consisting of gases, vapors, mists, or dusts may occur. <\/p>\n\n

International Classification: ATEX, NEC, and IECEx<\/h3>\n\n

There are no uniform international regulations governing explosion protection. In Europe, the ATEX Directives<\/strong><\/a> and the IEC\/EN 60079<\/strong> series of standards form the basis for the design and operation of explosion-protected systems. In the U.S., the National Electrical Code (NEC)<\/strong> and supplementary UL standards<\/strong> define the requirements for electrical equipment.IECEx<\/strong> complements these systems as an international certification system based on IEC standards and enables the worldwide recognition of tests and certifications for explosion-protected equipment and services. <\/p>\n\n

\"View<\/figure>\n\n

Classification of Explosive Atmospheres in Europe (ATEX)<\/h2>\n\n

In Europe, potentially explosive areas<\/a> are classified into three different zones<\/strong> based on the frequency and duration<\/strong> of explosive atmospheres, with this classification further distinguishing between gases, vapors, and mists on the one hand, and dusts on the other. This results in a total of six Ex zones<\/strong>. <\/p>\n\n

Ex Zones 0 and 1<\/h3>\n\n

Zone 0<\/strong> designates areas where an explosive gas atmosphere is present continuously or for long periods of time, such as inside containers or pipelines. In Ex Zone 1<\/strong>, an explosive gas atmosphere may occasionally occur during normal operation, for example at filling or emptying points. <\/p>\n\n

What is the Ex-Zone 2?<\/h3>\n\n

Zone 2<\/strong> is particularly relevant in practical applications. In this zone<\/strong>, an explosive gas atmosphere is expected to occur only rarely and for short periods, for example as a result of malfunctions or leaks. Many industrial applications\u2014especially those involving control cabinets and electrical components\u2014fall into this category. <\/p>\n\n

The legal regulations do not specify what \u201crarely\u201d means. In practice, however, the prevailing view is that even a single occurrence of an explosive atmosphere in a year requires an area to be classified as an Ex Zone 2. If the risk of explosion lasts for less than 30 minutes per year<\/strong>, this is generally referred to as a \u201cshort period.\u201d <\/p>\n\n

Ex-Zones 20, 21, and 22<\/h3>\n\n

Zones 20, 21, and 22 apply to combustible dusts. The basic principle is the same as that for gas zones, but it is adapted to the specific behavior of dust atmospheres. The key factor here is that dust deposits, dust clouds, and ignition sources behave differently than gases, which is why separate criteria apply for frequency and risk. <\/p>\n\n

An Overview of the Ex-Zones<\/h3>\n\n

The division into Ex zones is not merely a theoretical classification. It defines specific requirements for the design, selection, and use of electrical equipment and forms the basis for planning in accordance with standards. <\/p>\n\n

The zone classification shown below complies with the European ATEX system and the U.S. zone model according to NEC 505\/506<\/strong>:<\/p>\n\n

\"Overview<\/figure>\n\n

Explosion-Protected Zones: Guidelines, Laws, and Standards in the United States<\/h2>\n\n

An explosion at an industrial facility can have dangerous consequences. For this reason, the relevant regulatory authorities have enacted comprehensive regulations on explosion protection in general (zone classification, protective measures, etc.) and on the design and operation of electrical equipment in hazardous areas in particular. In the U.S., Articles 500 through 505 of the National Electrical Code (NEC) specify the requirements for equipment and installation intended for use in hazardous locations. These areas are referred to in North America as \u201cHazardous Locations,\u201d or \u201cHazLoc\u201d for short<\/a>. <\/p>\n\n

Zoning in the United States<\/h3>\n\n

The zoning system in the United States<\/strong> differs fundamentally from the European ATEX model. Traditionally, the Class\/Division system<\/strong> based on NEC 500<\/a> is used there, which distinguishes more clearly between types of substances and their properties. <\/p>\n\n

Ex Zones According to NEC 505: The Three-Zone Model<\/h3>\n\n

With the introduction of NEC 505<\/strong><\/a>,<\/strong> a zone model<\/strong> was also introduced<\/strong> in the U.S. that is<\/strong> based on the internationally standard three-zone classification (Zones 0, 1, and 2)<\/strong>. As a result, both systems now exist in parallel. <\/p>\n\n

Although the zone numbering is similar, the requirements, testing standards, and certifications<\/strong> are not identical to those of ATEX. Therefore, an Ex Zone 2 as defined by European standards<\/strong> is not automatically equivalent to a Zone 2 under NEC 505. <\/p>\n\n

Zone Classification in Explosion Protection: Practical Criteria<\/h2>\n\n

The classification of zones for explosion protection<\/strong> is based on a risk assessment. Key criteria include: <\/p>\n\n