ATEX, Intrinsic Safety & Hazardous Area Information

what the law says

If you are designing or manufacturing equipment for use in a potentially explosive atmosphere then ATEX directive (2014/34/EU) applies to you. Equally, if you are responsible for providing any workforce who will be subject to working in a potentially explosive atmosphere then ATEX 137 (1999/92/EC), will apply to you as an employer to assess explosion risks and implement explosion prevention and protection measures that will include making sure that any equipment present is suitable for that environment.

The engineering aspect

Overheating components, sparks and short circuits can all trigger an explosion in the right circumstances and this is where the Intrinsic Safety (IS) standard comes in. The Intrinsic Safety (IS) standard works with the ATEX directive by ensuring that no components or circuits can release enough energy to ignite a hazardous atmosphere. Equipment rated for Zones 0 and 1 locations, typically need to meet intrinsic safety standards as they must prevent ignition under both normal and fault conditions.

The ATEX directive does take into account how often the atmosphere, where the equipment is located, is in a potentially explosive state. This is categorised as one of three zones.

Zone	Hazard	Protection Concepts	Explanation of the categories
0	Where explosive gas or dust atmospheres are present continuously.	Exia	Device safety must be guaranteed even in case of rare device failures, e.g. simultaneous failure of two components.
1	Where explosive gas or dust atmospheres are present during normal operations.	Exib, Exia, Exd, Exe, Exp, Exm and Exo	Device safety must be guaranteed if frequent failures can be expected, e.g. failure of one component.
2	Where explosive gas or dust atmospheres are unlikely but possible.	All concepts suitable for Zone 0 & 1, plus Exn, EXic and Exo	Device safety must be guaranteed in normal operation.

ATEX rated equipment should always have an ‘Ex’ mark if it is being sold within the UK or the EU. In addition to this mark the label must clearly indicate what ‘zone’ the equipment is rated for. For markets outside the British/EU zone the IECEx Scheme is an internationally recognized certification standard for equipment used in explosive atmospheres.

If the equipment is rated as intrinsically safe then the mark will read Ex i if sold in the British or EU markets. Other letters following the ‘i’ will dictate exactly what explosive atmosphere the equipment is intended for and these are listed in the table below. The key for an example label is as follows:

Ex ia IIC T4 Ga

• Ex = Suitable for explosive atmosphere in Britain
• ia = Highest level of intrinsic safety, suitable for Zone 0
• IIC = Gas group (with IIC indicating a high-risk environment, such as hydrogen)
• T4 = Temperature class (maximum surface temperature)
• Ga = Equipment protection level for zone 0 use

Marking Element	Description
Ex	Indicates that the equipment is certified for explosive atmospheres in Britain and the EU, in accordance with ATEX and International Electrotechnical Commission (IEC) standards.
Protection Type (ia, ib, d, e, p, o, q, m, n, t)	Explosive Protection Technique: ia: Intrinsically safe (limits energy to prevent ignition) for Zones 0, 1 and 2. ib: Intrinsically safe (limits energy to prevent ignition) for Zones 1 and 2 d: Flameproof enclosure. e: Increased safety. p: Pressurization. o: Oil immersion. q: Powder filling. m: Encapsulation. n: Non-sparking. t: Protection by enclosure for dust. The suitability of these protection types is set out in standards such as EN 60079 series
Group I / II	Equipment Group: Group I: For mining (underground, with methane presence)*. Group II: For above-ground industries with explosive gases, vapours, or dust. *Please refer to the following table for an explanation of mining categories M1 and M2
Gas Group (IIA, IIB, IIC)	Explosion Gas Group: IIA: Common flammable gases (propane). IIB: Ethylene. IIC: Hydrogen or acetylene (highest risk gases).
Temperature Class (T1 - T6)	Maximum surface temperature of equipment in normal use: T1: Up to 450°C. T2: Up to 300°C. T3: Up to 200°C. T4: Up to 135°C. T5: Up to 100°C. T6: Up to 85°C.
Protection Level (Ga, Gb, Gc, Da, Db, Dc) G for gas D for dust	Equipment Protection Level (EPL): Ga: Very high (Zone 0). Gb: High (Zone 1). Gc: Normal (Zone 2). Da: Very high (Zone 0). Db: High (Zone 1). Dc: Normal (Zone 2).
IP Code (IPxx)	Ingress Protection Rating, showing resistance to dust and moisture (IP65, IP67, etc.).

Category	Suitable Zones	Protection Requirements	Typical Equipment Examples
M1	Mines with continuous risk (Zone 0 equivalent)	Equipment must maintain safety and function during operation, even in the presence of an explosive atmosphere. Must remain operational in case of equipment fault.	Main ventilation systems, emergency lighting, communication devices, power systems.
M2	Mines with occasional risk (Zone 1 equivalent)	Equipment may need to be turned off if an explosive atmosphere is detected. Does not need to operate continuously in explosive conditions but must be robust to withstand normal use.	Drilling machines, mining vehicles, conveyors, pumps.

How we can help

We frequently work with end users and equipment suppliers to ensure that any sensor made by us, for use in an explosive atmosphere, is ATEX compliant. We can help you specify the sensor that you need for your particular set up and manufacture them at our production facility in Reading. We provide a comprehensive range of ATEX rated pressure sensors and wireless data equipment. In addition, many of our other sensor products can be made specifically to be ATEX compliant too.

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Characteristics of Substances

Flashpoint

This is the lowest temperature at which a liquid generates sufficient vapour to support ignition. This vapour can be ignited in many ways including temperature or energy (i.e. a spark).

Ignition Temperature

This is the lowest temperature at which the vapour will be ignited. This defines the temperature class.

Classification of Maximum Surface Temperatures of Electrical Apparatus (CENELEC)

Temp. Class	Max. Surface Temp.
T1	<450ºC
T2	<300ºC
T3	<200ºC
T4	<135ºC
T5	<100ºC
T6	<85ºC

Characteristics Of Some Common Flammable Materials

Gas/Vapour	Flashpoint	Gas Group	Ignition Temp.	Temp. Class
Acetone	19ºC	IIA	535ºC	T1
Butane	-60ºC	IIA	365ºC	T2
Heptane	-4ºC	IIA	215ºC	T3
Ethyl Methyl Ether	37ºC	IIB	190ºC	T4
Note: There is no connection between ignition energy and ignition temperature

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Related Products

• ATEX / Intrinsically Safe Pressure Sensors
• ATEX / Intrinsically Safe Load Cells