Ex zone - what is it?

An ex zone refers to a potentially explosive atmosphere. The risk is particularly present where explosive substances such as dusts, liquids or gases are produced, processed, transported or stored.

What is Ex?

The Ex mark is part of the safety marking. It indicates that an explosive atmosphere, i.e. a risk of a potential explosion, may occur in or near a building. It should be displayed in a prominent position.

Ex zone – requirements

This space requires appropriate measures. The employer is obliged, among other things, to:

• designate Ex areas

• avoid sources of ignition in these areas

• prevent the consequences of a possible explosion

• document explosion protection

Potentially explosive atmospheres - demarcation

A potentially explosive atmosphere is an area where it is possible that an explosive mixture (of at least 0.01 m3 volume in a confined space) can occur whose explosion would cause a pressure increase of at least 5 kPa.

An explosion will not occur if the flammable substance in a mixture with air takes values below the lower explosive limit and above the upper explosive limit.

Division model

The division model is mainly used in the United States and Canada, while the rest of the world generally uses a zone system. Division 2 corresponds to zone 2, while Division 1 is either zone 0 or 1.

Potentially explosive atmospheres - classification

The division of explosion danger zones is made on the basis of the probability and duration of occurrence of an explosive atmosphere.

• Zone G - the atmosphere contains (or has the risk of containing) explosive liquid, vapour or gas
• Zone D - an explosive atmosphere contains (or there is a risk of containing): explosive solids, fibres or dust particles, including but not limited to: granules, wood fibres and saw dust, animal feed
• Zone 0 - explosive atmosphere present continuously, min. 1000 hours per year
• Zone 1 - explosive atmospheres occur frequently, between 10 and 1000 hours per year
• Zone 2 - workers are not exposed to explosive atmospheres during normal work. When it occurs it persists for a short period of time, less than 10 hours per year

Dust, powder and fibre zones

• Zone 20 - an explosive atmosphere in the form of a flammable dust cloud is present continuously, or for long periods or frequently
• Zone 21 - an explosive atmosphere in the form of a cloud of combustible dust may occur in normal operation from time to time
• Zone 22 - a place where during normal operation an explosive atmosphere in the form of a cloud of combustible dust in air is unlikely to occur. If it does occur, it will be rare and brief.

Temperature and humidity sensors for Ex zones

The JUMO PROCESStemp resistance sensor has ATEX and IECEx approvals for hazardous areas. It is ideal for use in hazardous environments due to its robust housing made of stainless steel, titanium, tantalum, Inconel® or HASTELLOY®, an operating temperature of up to 600°C and an IP65 protection rating.

About the Author

My name is Saskia van der Laan and I have been working at JUMO for quite some time, combining my professional skills with my passion for writing. Always with the aim of using written text to translate technology into practice and to inform and inspire the reader. In my spare time, I like to do sports and enjoy a long walk with the dog.