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Explosion Protection Basics

Many industrial processes involve flammable materials that can create a potentially explosive atmosphere. Such atmospheres occur when gases, vapours, dust, or other flammable substances mix with air, posing a risk of ignition.

To safeguard both people and equipment, it is essential to ensure that electrical systems and devices cannot ignite these hazardous environments. This means taking proactive measures to eliminate all possible sources of ignition that could trigger an explosion.

What is an Explosion?

An explosion is an uncontrolled combustion event that causes a sudden rise in temperature and pressure. For an explosion to occur, three elements must be present:

Fuel – such as a flammable gas or vapor

Oxidiser – typically the oxygen in air

Ignition source – for example, an electrical spark or hot surface

A potentially explosive atmosphere forms when fuel and oxygen mix within a specific concentration range, known as the explosion limits. These limits vary depending on factors such as air pressure, oxygen levels, available energy, and the size of the confined space.

Mixtures outside these limits will not ignite—but they can quickly become explosive if conditions change.

Ignition Sources

An explosive atmosphere can be triggered by a variety of ignition sources. Common examples include: 

  • Electrical arcs and sparks
  • Flames and hot surfaces
  • Static electricity
  • Electromagnetic radiation
  • Chemical reactions
  • Mechanical impact or friction
  • Compression ignition
  • Acoustic energy
  • Ionising radiation

Each of these has the potential to ignite flammable mixtures, making strict control and prevention essential for explosion protection.

ATEX Directive – EU Legislation

The ATEX regulatory framework ensures safety in potentially explosive atmospheres across the EU. Here’s what you need to know:

  • Equipment Directive (2014/34/EU)
    This directive, also known as ATEX 114, defines the essential requirements for equipment and protective systems used in explosive environments. It came into force on 20 April 2016, replacing the previous 94/9/EC directive.
  • Workplace Directive (1999/92/EC)
    Known as ATEX 137, this directive requires employers to perform comprehensive risk assessments, classify hazardous zones, and implement preventive safety measures to protect workers.

Recent Updates to Be Aware Of:

  • A new EU directive (2024/2749) mandates changes to conformity assessments and must be adopted by 29 May 2026, taking effect from 30 May 2026.
  • The 5th Edition ATEX Guide (April 2024) provides updated guidance, including how to align with the Machinery Regulation (EU 2023/1230), particularly around digital technical documentation.
  • Updated harmonised standards took effect in April 2025, including EN 14983:2024, with a 1.5-year transition window for manufacturers.

What the ATEX Directive Covers

The ATEX Directive (2014/34/EU, also called ATEX 114) applies to a wide range of products used in potentially explosive atmospheres. It covers:

  • Equipment – products with their own potential ignition source (e.g., motors, sensors, or control panels).
  • Protective systems – products designed to stop or control the effects of incipient explosions (e.g., explosion vents or suppression systems).
  • Safety devices – products, sometimes located outside the hazardous area, that provide explosion safety functions (e.g., monitoring or shut-off systems).
  • Components – products intended to form part of equipment or protective systems.

To be placed on the EU market, equipment must:

  • Meet the essential health and safety requirements outlined in the Directive.
  • Undergo appropriate conformity assessment procedures.
  • Carry the CE marking and the specific ATEX marking (Ex symbol).
Beyond Europe – International Standards

While ATEX is the standard across the EU, many countries outside Europe (and in the Americas) rely on the IECEx system or adopt IEC standards as their national framework. These systems share many similarities but are not identical, and certification is not automatically interchangeable. 

Important Notes

This section provides general guidance only. When selecting, installing, or maintaining equipment for explosive atmospheres:

  • Always consult relevant regulations, codes of practice, and harmonised standards.
  • Seek expert advice to ensure compliance before equipment is put into service or repaired.
  • Be aware of key differences between European ATEX certification and American/North American approvals (such as NEC/CEC Class & Division or Zone systems).

Update (2024–2025):

  • The latest list of harmonised EN standards under ATEX was updated in April 2025 (e.g., EN 14983:2024). Manufacturers have a 1.5-year transition period to adapt.
  • A new EU Directive (2024/2749) introduces changes to conformity assessments and will apply from 30 May 2026.
  • The 5th Edition of the ATEX Guide (April 2024) aligns ATEX with the new EU Machinery Regulation (2023/1230), including provisions for digital documentation.

Area Classification (Zoning)

When ignition sources cannot be eliminated, and flammable gases, vapours, mists, or dusts may be present, it is essential to assess both the extent and duration of the risk. This process is known as Area Classification, or more commonly, Zoning.

Why Zoning Matters

Zoning provides the foundation for selecting the right equipment and protection methods. By defining how often and for how long an explosive atmosphere may be present, businesses can ensure the correct level of safety and compliance.

How Areas Are Classified

Areas are classified based on:

  • The properties of the flammable substance (gas, vapour, mist, or dust)
  • The likelihood of it being present in sufficient concentration to cause an explosion
  • The duration of its presence

Under ATEX and IECEx, zones are defined as follows:

Gas / Vapour Atmospheres

  • Zone 0 – Continuous or long periods of explosive atmosphere present
  • Zone 1 – Likely to occur occasionally during normal operation
  • Zone 2 – Unlikely to occur, and if so, only for short periods

Dust Atmospheres

  • Zone 20 – Continuous or long periods of combustible dust present
  • Zone 21 – Likely to occur occasionally during normal operation
  • Zone 22 – Unlikely to occur, and if so, only for short periods
Updates & Best Practice (2024–2025)

The 5th Edition ATEX Guide (April 2024) includes new guidance on aligning zoning with the EU Machinery Regulation (2023/1230).
Harmonised EN standards for area classification, such as EN 60079-10-1 (gases) and EN 60079-10-2 (dusts), remain the key references, with periodic updates to reflect IECEx standards.
IECEx and many national regulators also recognise risk-based classification approaches, especially in complex facilities where traditional zoning may be conservative.

Temperature Classification (T-Rating)

Every flammable gas or vapor has an auto-ignition temperature – the point at which it will ignite spontaneously without any external ignition source. If equipment surfaces reach or exceed this temperature, they can ignite an explosive atmosphere.
To prevent this, electrical and non-electrical equipment intended for use in hazardous areas is assigned a Temperature Class (T-Class). This indicates the maximum surface temperature the equipment can reach in normal service.

Key Points:

  • T-Class ratings are compared against the auto-ignition temperature of the flammable substance present.
  • If the maximum surface temperature of the equipment is lower than the gas’s auto-ignition temperature, the equipment is considered safe for use.
  • Ratings are typically based on an ambient temperature of 40 °C (102 °F), unless otherwise stated. Some modern equipment may carry ratings up to +60 °C or higher depending on certification.
  • Correct T-Class selection helps ensure that even during normal operation, flammable releases cannot be ignited by hot surfaces.

Standard Temperature Classes (for gases/vapors)

T-Class Maximum Surface Temperature
T1 450 °C
T2 300 °C
T3 200 °C
T4 135 °C
T5 100 °C
T6 85 °C

Ex Equipment Updates (2024–2025)

  • Recent IEC/EN 60079-0 revisions allow for higher ambient temperature ratings (e.g., +55 °C or +60 °C), which must be clearly marked on the equipment label.
  • Both ATEX and IECEx systems require clear documentation of equipment temperature limits as part of the Ex-marking.
  • Users must always confirm equipment certification against site-specific conditions, including ambient temperature variations, dust layering, and cooling limitations.

Selecting Electrical Equipment for Hazardous Areas

When choosing equipment for use in potentially explosive atmospheres, several key factors must be considered to ensure both safety and regulatory compliance. Equipment selection is typically based on:

  • Hazardous Area Classification (Zoning) – Defines the likelihood and duration of an explosive atmosphere being present.
  • Temperature Class (T-Class) or Ignition Temperature – Ensures equipment surface temperatures remain below the auto-ignition point of nearby gases, vapours, mists, dusts, or fibres.
  • Gas, Vapour, or Dust Group – Equipment must be certified for the correct group (e.g., IIA, IIB, IIC for gases or IIIA, IIIB, IIIC for dusts) depending on the explosion risk.
  • External Conditions & Ambient Temperature – Equipment ratings must match the environmental conditions, including higher or lower ambient temperatures, dust accumulation, humidity, or corrosive atmospheres.
  • Geographical Destination & Certification Scheme – Equipment must carry certification from the relevant body (e.g., ATEX in the EU, IECEx internationally, NEC/CEC in North America, INMETRO in Brazil, UKEX in the UK).

Standards & Best Practice Updates (2024–2025)

  • Global alignment: ATEX (EU), IECEx (international), and UKEX (UK) are increasingly harmonised, but regional requirements (e.g., NEC/CEC in North America) still differ. Always verify against local regulations.
  • Higher ambient ratings: Recent updates to IEC/EN 60079-0 allow for equipment certified up to +55 °C or +60 °C, which must be clearly marked.
  • Digital conformity documentation: The new ATEX 5th Edition Guide (2024) supports digital formats for technical documentation and marking.
  • Emerging markets: Countries in Asia and South America are adopting IECEx or hybrid schemes but may require local approvals in addition to IECEx certificates.