A-Z of ATEX Concepts

Understanding ATEX concepts can be a bit of a minefield when there are so many terms and a huge amount of jargon thrown around. With changing legislation, relating to protection levels, certification and deadlines around labelling and certifications, we completely understand when our customers don’t have the information required to complete an accurate fan selection. In this article we’re covering some common terms in simple, layman terms, to help you to get your head around explosive atmospheres. Please bear in mind that the term ATEX will be superseded by the term UKEX in the foreseeable future and as such can be read interchangeably. For now, we’ll continue to use the term ATEX when referring to information covered in the directives.  

ATEX: An anagram of the French, Atmosphere Explosibles. It is the name commonly given to the two European directives for controlling explosive atmospheres; 99/92/EC and 2014/34/EU with the latter relating to supplied equipment.  


“b” protection meaning increased safety on electrical components such as motors. Namely Ex eb.  


Category: Categories are used to simplify ATEX equipment selection. The 6 ATEX categories are 1, 2 and 3 representing High, medium and low risk respectively, each with either G (gas) or D (dust) to represent the characteristics of the atmosphere.  


Clearances: Clearances between the rotating elements and the fan casing are the most important safety features of any industrial fan construction.  


DSEAR: The dangerous substances and explosive atmospheres regulation 2002 is a UK law that requires professionals to control and mitigate workplace risks of fire, explosion, and metal corrosion caused by hazardous substances. The regulation is applicable to workplaces where dangerous substances are stored, used or produced. Failure to comply to DSEAR can lead to costly fines and work-related injuries.  


EN 14896:2017: Known as the “Design of fans working in potentially explosive atmospheres” legislation that specifies the constructional requirements for fans constructed in Group IIG of explosion groups IIA, IIB and IIC for use in explosive atmospheres.  


Flameproof: in flameproof Exd equipment, the housing will contain a flame without allowing it to escape to the hazardous atmosphere. Suitable for zones 1 and 2, category 2 and 3 unless they have a second character a, b or c which further limits this.  


Group: Explosive gases and dusts are grouped together according to their potential to cause an explosion. This is based on its likelihood to be ignited along with a few other things; minimum ignition energy, minimum ignition temperature, auto ignition temperature, layer ignition temperature.  


Ex h: Non-electrical components of complete fan assemblies must be ATEX certified according to the directive. Ex h indicates that the fan construction Is suitable for explosive atmospheres.


Hazardous Area Classification: A hazardous area classification is undertaken by an ATEX consultant who will assess the environment to determine the likelihood of an explosion occurring. From here they will allocate the areas ATEX gas and dust zones accordingly.  


Ignition: A potentially explosive atmosphere that can coupled with a source of ignition can create an explosion. There are many sources of ignition, some can happen because of electronic failure, mechanical failure, or the friction of an impeller with the inlet causing static discharges.  


January 2025: From the 1st January 2025, there will be a legal provision for UKCA marking and labelling on all equipment placed on the UK market. The previous deadline was January 2023.  


LFL: Known as the lower flammability limit, the lowest concentration (percentage) of a gas or a vapor in air capable of producing a flash of fire in the presence of an ignition source (arc, flame, heat). The term is considered by many safety professionals to be the same as the lower explosive level (LEL). We discuss this in the following article: Ventilation & Dilution of Hydrogen Leaks with Exhaust Fans.  


Maximum Surface Temperature: The maximum surface temperature of the fan characterises the hottest part of the equipment that can come in to contact with the explosive atmosphere or the maximum temperature of the conveyed atmosphere (flammable or not) which can act as an ignition source. If the temperature on the surface of the motor exceeds this level, ignition of either the gas or dust is possible.  


Non-sparking equipment Ex Na: Former Ex Na markings are now known as Ex ec meaning increased safety. This is classed as the lowest and normal level of Ex protection, also known as reduced risk protection and for motors is non-sparking. The design aims to prevent an internal malfunction from creating sparks in normal operation and therefore is not capable of causing an explosive atmosphere to ignite.  


Oxygen: When explosive substances mix with Oxygen in vapour densities in the Upper explosive limits, an explosion may occur. Lots of elements are lighter than oxygen and can accumulate in ceiling voids if not ventilated appropriately.  


Protection Level: The protection level of equipment (EPL) is defined by international standards and indicates the likelihood that the equipment can become a source of ignition. There are three standard protection levels: a, b and c.  


Quality Assurance Notification (QAN): A manufacturers quality system need to be certified in compliance with the requirements for the ATEX Directive. This is compulsory for category 1 and 2 products.  


Rubbing Friction: Metal to metal ignition is caused either by rubbing friction, as mentioned earlier, such as between a rotating impeller and a stationary piece of metal, or by impact of two metal objects. Legislation on ATEX fan construction indicates that there must be sufficient clearances to prevent the rotating impeller and stationary pieces of metal, say on the casing, from touching.  


Static Discharge: Mechanical sparks and friction are one of the most common causes of ignition of flammable gases and dust clouds. Ignition sources can arise from the electric discharge of static electricity when using non-conductive materials. Permissible material pairings on ATEX fans prevents static discharge.  


Temperature Class: A range of classes that indicate a gas or dusts ignition temperature. Temperature classes range from T1 (the hottest) to T6. This determines the maximum surface temperature allowed to prevent ignition.  


UKEX: The UK alternative to ATEX adapted as a standard post the UK leaving the European Union/BREXIT. During this transition EU directives were adopted into UK legislation to ensure the safe placement of equipment for potentially explosive environments. This meant readdressing CE quality marking to UKCA and UKEX being a part of the UKCA process.  


Vapour Density: Vapour density of a gas is given relative to that of air. Many gases, such as Hydrogen are lighter than air. Any vapour release will rise and dilute rapidly. When indoors, these gases will collect in the roof space. Where gases are heavier than air they will fall to the lowest point and fill sumps, trenches, or hollows in the ground. These gases can remain there long after the release has been stopped and continue to pose a danger.  


Zone: Gas and dust zones are used to categorise an environment according to the presence of an explosive substance. There are three gas zones that indicate presence; 0, 1 and 2 where zone 2 indicates the presence of an explosive gas would be in abnormal circumstances. We supply fans for gas zones 1 and 2. There are three dust zones; 20, 21 and 22. We offer industrial fans to dust zone 22. 


For a more in-depth understanding of the above terms, click through to read the specific articles on each subject. To view our wide range of ATEX certified fans you can download the literature below.