Not every enclosure for Ex zones works the same way – find out how Ex d, Ex e, and Ex i differ.

Are you looking for the right enclosure for a potentially explosive atmosphere and don’t know whether to choose Ex d, Ex e or Ex i? You’ve come to the right place. In this guide, we show you the differences between popular explosion protection methods, how they work and when to use them to meet ATEX requirements and ensure real safety. 

What exactly do Ex d, Ex e and Ex i mean? Don’t be confused by the markings!

These are designations for various methods of protecting equipment in potentially explosive atmospheres. Each one works differently and is intended for different applications.

In brief:

• Ex d – flameproof protection, an explosion may occur inside the enclosure, but it does not escape outside,
  
• Ex e – increased safety, design prevents sparking or overheating,
  
• Ex i – intrinsically safe, the energy in the circuit is limited to a level that cannot cause ignition, even in the event of a short circuit.
  

Which method you should choose depends on the type of installation, the level of risk and the Ex zone classification. This is where the most common mistake occurs – selecting the type of protection “by eye”. Meanwhile, each method has its own technical documentation, performance standards and limitations.

It is not enough to know how explosion-proof enclosures work – it is also important to understand what actually causes an explosive atmosphere to ignite. If you want to find out how much energy is needed to cause a dust or gas explosion, check out our article on minimum ignition energy.

Why does Ex d “contain the explosion inside”, while Ex e does everything possible to prevent it from happening?

Because these are two completely different approaches to securing equipment in Ex zones. Ex d allows an explosion to occur – but stops it. Ex e is designed to prevent any source of ignition from occurring in the first place.

Quick comparison:

• Ex d – flameproof protection, thick walls, extinguishing gaps, withstands explosion pressure,
  
• Ex e – greater spacing, no spark sources, controlled temperature, no arcs or overloads.
  

The choice depends on what type of device you have and in which zone it is to operate. Motor? Probably Ex d. Lighting fixture? Ex e is often sufficient. Do you have a mixed system? It may turn out that you need to combine both solutions in one installation.

Do you have sensors, terminals or modules? Check whether you need Ex i

If you work with sensors, transducers or signalling devices, you should most likely use Ex intrinsically safe circuits. This solution limits the energy in the circuit to a harmless level, even in the event of a short circuit or failure.

Why it’s worth it:

• Ex i eliminates the need for bulky enclosures – the entire safety system is based on energy barriers,
  
• meets the requirements for zones 0, 1 and 2 (in versions ia, ib, ic),
  
• It is ideal for industrial, process and measurement automation.
  

Typical applications include:

• temperature, level, flow and pressure sensors,
  
• analogue and digital converters,
  
• communication interfaces and industrial buses.

That’s not all – learn about other explosion protection methods and find out where they are used.

Ex d, Ex e and Ex i are only some of the available methods. The EN 60079 series of standards provide for many more ways of protecting equipment in Ex zones – often overlooked, but very useful in specific situations.

Also worth knowing:

• Ex m – protection by flooding with insulating compound (e.g. electronic modules),
  
• Ex p – overpressure protection, keeping clean air or gas inside the enclosure (e.g. control cabinets),
  
• Ex o – protection by immersion in oil (less common, but still acceptable),
  
• Ex q – protection by powder filling (mainly used in niche applications).
  

Each of these methods is permitted by the ATEX directive and has its place. For example, Ex p is used where a standard enclosure would be too large or expensive, but Zone 1 requirements still need to be met. Ex m and Ex q allow sensitive components, such as measurement electronics, to be protected without changing their original design.

If you are planning to install automation in Ex zones, it is worth knowing the alternatives and choosing a method not only according to the level of risk, but also according to the environment, operation and maintenance costs. Sometimes a less obvious solution turns out to be the most appropriate – both technically and economically.

When is one enclosure not enough? How to combine different types of protection in a single installation

In many cases, the use of a single explosion protection method is not sufficient. In modern automation systems or installations consisting of components with different functions, it is necessary to combine several types of protection. This does not mean mixing them arbitrarily, but rather compliance with standards, continuity of certification and installation safety.

The most common combinations are:

• Ex d + Ex e – for switchgear where some components (e.g. relays) may explode and some should not cause ignition,
  
• Ex i + Ex m – for signal modules, sensors and encapsulated electronics,
  
• Ex e + Ex t – particularly in dusty environments, where surface protection is added,
  
• Ex d + Ex i – where the device performs switching operations and simultaneously receives signals from intrinsically safe circuits.
  

Important:

• each component must have the appropriate certificate and EPL level in accordance with the target zone,
  
• Transitions between enclosures must be properly designed, often using Ex partitioning glands or separation barriers.
  
• Ex circuits must not be connected to other types without observing the rules of galvanic separation – this is a common mistake leading to the loss of intrinsic safety.
  

When designing such an installation, it is crucial to comply with PN-EN 60079-14, use clear markings on the enclosures, and provide accurate zone and operating documentation. A seemingly simple layout can become problematic if you do not take into account all the interdependencies between protection methods.

It works in theory, but how does it work in practice? Common mistakes when using Ex and Ex d enclosures that can cost you dearly

Even the best-chosen enclosure will not protect the installation if it is installed incorrectly or selected without taking into account the specific characteristics of the area. In practice, the most common problems are minor details that are not visible at first glance but have serious consequences.

List of common mistakes:

• Incorrect length or type of cable glands – especially for Ex d enclosures, where this affects pressure resistance.
  
• failure to maintain separation for Ex circuits and – running signal cables together with power cables is a critical error,
  
• cables without the appropriate certification or temperature resistance – which excludes compliance with EPL,
  
• no internal seals or replacement of structural components – which automatically invalidates the ATEX certificate.
  

The following are also often overlooked in Ex d enclosures:

• checking the tightening torques of fastening screws that are important for maintaining gas tightness,
  
• incorrect selection of temperature class, causing the enclosure to heat up above T5/T6, exceeding the permissible values for an explosive atmosphere.
  

These are not errors that can be corrected at the last minute. They may result in the need for recertification, loss of approval to work in an Ex zone or, in the worst-case scenario, a real risk of explosion.

Therefore, regardless of whether you are designing, installing or auditing, it is important to be aware of these pitfalls and not treat explosion protection as a formality. In Ex zones, errors are not corrected – they are avoided from the outset.

Choosing the right type of explosion protection is not just a technical issue – it is a decision that affects safety, regulatory compliance and service costs for many years to come. 

We support you at every stage: from Ex zone analysis and solution selection to ATEX-compliant documentation. We supply certified Ex d, Ex e and Ex i enclosures, complete with full specifications and assistance with integration into your existing installation.

If you have doubts about whether your current safety measures are adequate, we can conduct an ATEX audit and identify areas for improvement before a hazard arises.

FAQ

What is the difference between Ex d and Ex e?

Ex d is a flameproof enclosure – it is assumed that an explosion may occur, but it will be contained inside. Ex e is an increased safety enclosure – its design prevents sparks or overheating.

What is Ex protection used for?

Ex i, or intrinsic safety, involves limiting the energy in the circuit to a level that cannot cause ignition, even in the event of a short circuit. It is most commonly used in automation and sensors.

Can I combine different types of protection in one installation?

Yes, but only if compliance with standards (e.g. PN-EN 60079-14) is maintained, and the appropriate components and documentation are selected. Care must also be taken to ensure that the entire system is separated and certified.

What standards govern explosion-proof enclosures?

The basic ones are: EN 60079-0 (general requirements), EN 60079-1 (for Ex d), EN 60079-7 (for Ex e), EN 60079-11 (for Ex i). All refer to the ATEX Directive 2014/34/EU.

Is every ATEX-certified enclosure suitable for my zone?

No. The enclosure must be selected for a specific zone (e.g. 1, 2, 21, 22), explosion group (IIA, IIB, IIC) and EPL protection level. It is also worth paying attention to the temperature class and type of application.