Components for Explosion Hazard Areas – Safety Rules in Explosive Atmospheres

An explosion hazard area is a space where an explosive atmosphere can occur continuously, periodically, or occasionally. In such areas, components for explosion hazard zones must comply with strict safety rules, and every electrical, mechanical, or protective element is selected based on the ATEX directive and a detailed classification of zones. This article will discuss what Ex zones are, how an explosive atmosphere is formed, which devices are intended to operate in such areas, and how to correctly select components that will not become an ignition source.

What are explosion hazard zones – zone classification

An explosive atmosphere occurs when a mixture of flammable gases, dusts, liquids, or mists is present in the air at a concentration that can lead to ignition. Ex zones are classified based on the frequency of hazard occurrence, and their designations are crucial for selecting devices and protective systems.

Gas zones

• Zone 0 – an explosive atmosphere containing a mixture of flammable substances with air is present continuously or for long periods.
• Zone 1 – an explosive atmosphere occurs periodically under normal operating conditions.
• Zone 2 – an explosive atmosphere occurs occasionally or for a short period.

Dust zones

• Zone 20 – an explosive atmosphere in the form of a combustible dust cloud occurs continuously or frequently under normal operating conditions.
• Zone 21 – the hazard occurs regularly, but not continuously under normal operating conditions.
• Zone 22 – an explosive atmosphere in the form of a combustible dust cloud occurs occasionally under normal operating conditions.

ATEX Directive – the foundation of safety in explosive environments

The ATEX directive specifies the requirements for devices and protective systems intended to operate in explosion hazard zones. Ex devices must be designed according to the standard, tested, and marked to indicate resistance to ignition in explosive atmospheres.

Device categories

• Category 1 – devices for zones where an explosive atmosphere may occur continuously or for long periods, requiring the highest level of protection (zones 0 or 20).
• Category 2 – devices for zones 1 and 21.
• Category 3 – devices for zones 2 and 22.

Ex markings

• ex d – flameproof enclosure,
• ex e – increased safety,
• ex i – intrinsically safe, used in electrical circuits so that electrical energy can never ignite an explosive atmosphere.

Ex zones in practice – how an explosive atmosphere forms

An explosive atmosphere can form due to the presence of:

• flammable gases,
• organic or metallic dusts,
• volatile liquids,
• flammable mists,
• explosive mixtures in industrial processes.

For an explosion to occur, the flammable substance must be present in the air at an appropriate concentration (between the lower and upper explosive limits, LEL and UEL) and an ignition source must be present. Ignition sources can include electric sparks, hot surfaces, electrostatic charges, mechanical friction, flames, electric arcs, and certain chemical reactions.

Components for explosion hazard zones – requirements

Devices intended for use in explosive atmospheres must meet a number of requirements to prevent ignition:

• Surface temperature control – components must not reach temperatures capable of igniting gases or dusts.
• Elimination of electric sparks – the design of protective systems must prevent sparks from occurring, both internally and externally.
• Resistance to environmental conditions – in industrial production, devices often operate in harsh conditions, and explosive atmospheres require stable and reliable component performance.
• Compliance with device category – replacements, repairs, and system design must comply with the ATEX directive and ex markings.
• Certification and documentation – every component used in an Ex zone should have an ATEX certificate confirming that it has undergone a rigorous assessment process.

Working in explosion hazard zones – which devices to use?

In explosion hazard areas, the following are used:

• electrical devices in Ex design,
• control systems with explosion protection,
• gas and dust sensors in Ex version,
• protective enclosures with an appropriate protection class,
• electrical installation components intended for operation in explosive atmospheres,
• protective components preventing overheating and sparks.

These devices must be intended for operation in a specific Ex zone, have appropriate markings, and be designed so that they do not become an ignition source in the event of a failure or overload.

Ex markings – what the symbols mean

ATEX markings allow you to determine:

• type of protection,
• device category,
• type of explosive atmosphere (gas, dust),
• temperature class,
• explosive group of the mixture.

For example, the Ex marking indicates that the device has been manufactured according to explosion protection principles and is intended for use in zones where explosive mixtures occur.

Summary – safety starts with proper component selection

Explosion hazard zones require the use of devices and protective systems specifically designed for operation in such conditions. Understanding zone classification, ATEX directive rules, and what Ex zones are in industrial practice is key. Only properly selected devices for explosion hazard zones ensure the protection of people, infrastructure, and industrial processes.

We invite you to explore our offer. We provide support in selecting the right components for demanding applications.