Regulatory Compliance in Dust Hazard Management – Meeting ATEX and DSEAR Standards

Combustible dust hazards pose significant risks in industrial environments, making dust hazard management and regulatory compliance critical aspects of process safety management.

The ATEX (Atmosphères Explosibles) directives and the DSEAR (Dangerous Substances and Explosive Atmospheres Regulations) establish strict requirements for identifying, assessing and mitigating dust explosion risks.

An in-depth understanding of these regulations reveals key compliance steps, risk assessment methodologies, and control measures aimed at minimising dust-related hazards. Practical approaches to zoning classification, explosion protection, and documentation requirements are also examined, helping industries align with legal obligations while enhancing workplace safety.

As enforcement tightens and penalties for non-compliance grow, adopting a proactive regulatory strategy is essential for operational continuity and risk reduction.

What is DSEAR/ATEX and what does it really want me to do with my dust hazards?

DSEAR and ATEX came into force in 2003 and relate to dust hazard management and the protection of workers in workplaces handling any dust, whether in the form of solid particles or fibrous materials or otherwise, which can form an explosive mixture with air or an explosive atmosphere.

Many of the underlying principles for compliance had been in practice within industry for many decades before, however the ATEX directive set a requirement for EU member states to enshrine such practices into law. Most EU member states adopted ATEX directly, and in the UK it was adopted as DSEAR (Dangerous Substances and Explosive Atmospheres Regulations).

When it comes to DSEAR and ATEX most people are familiar with concepts such as hazardous area classification and the use of specially certified (EX) equipment within said areas. Whilst these are key elements of DSEAR and ATEX compliance, they are just that, elements. If we were to zoom out and look for a headline objective for DSEAR/ATEX, it can be summarised as follows (as per the UK’s HSE approved code of practice L138):

“to assess all potential risks to employees and others whose safety may be affected by the use or presence of a dangerous substance at the workplace.”

This means we must understand to a suitable and sufficient extent the likelihood of fire/explosion events and their anticipated effects which could result from handling dangerous substances.

At a high-level, compliance with DSEAR/ATEX means demonstrating that the risks associated with handling combustible dusts are acceptable and have been reduced to as low as is reasonably practicable. The measures we use to reduce risk must then also be applied as per a strict hierarchy:

1. Do not have a flammable atmosphere, but if you do…
2. Do not ignite it, but if you do…
3. Do not hurt anyone.

Figure 1: Optically dense dust cloud

Know your material and process

To demonstrate compliance and ensure effective dust hazard management, we must first lay a solid foundation. This foundation is formed of a solid understanding of our processes/activities and the materials we are handling in order to define normal operation.

Whilst this sounds simple, it often proves a big blocker when completing an assessment and demonstrating compliance.

Dusts, unlike their liquid and gas counterparts, can be a little bit more unpredictable when it comes to physical properties. This is because solid materials can be the same chemically but have different properties due to variations in the particulate form.

Particle size, morphology, density and moisture content can all have a significant impact on the ability of a dust to form flammable atmospheres, its sensitivity to ignition and the severity of consequences should an ignition occur.

It is also because of these anticipated variations that suppliers of powder material will seldom provide the required data for a DSEAR/ATEX assessment, and instead testing or more rigorous literature searches are required.

Key material information for DSEAR/ATEX assessments are material dispersibility (in air), particle size, combustibility (A/B testing), minimum explosible concentration, minimum ignition energy, minimum ignition temperature and layer ignition temperature.

Additional data points may be required such as conductivity or explosion severity, however their relevance will be dependent on the strategy of prevention/protection deployed.

Figure 2:Hartmann tube used for laboratory dust flammability testing

When it comes to process information, there needs to be sufficient to ensure that we are able to identify where dusts could be present during both normal and abnormal operation.

Understanding and reducing the likelihood of explosive atmosphere formation

The second step, and perhaps the more defined step towards DSEAR/ATEX compliance and effective dust hazard management, is identifying where and when explosive atmospheres may form within our process. It is within this step that hazardous area classification is mandated.

Hazardous area classification is essentially a structured approach that places identified explosive atmospheres into four pots based on likelihood:

• Those that arise frequently during normal operation – Zone 20
• Those that arise only occasionally during normal operation – Zone 21
• Those that arise only during expected abnormal operation and for short periods of time – Zone 22
• Those that only arise as a result of rare (or less likely) failure whereby formal hazardous area classification is not required – Non-hazardous

Furthermore, the dispersion of an explosive atmosphere is also evaluated to estimate the extent of the identified hazardous areas.

The core standard and methodology for conducting hazardous area classification for dusts is BS EN 60079: Explosive atmospheres – Part 10-2: Classification of areas – Explosive dust atmospheres.

Housekeeping is King when Working with Dusty Processes

Good housekeeping is vital in dust hazard management, helping to prevent dust explosions in the workplace. Dust layers are extremely dangerous and are known as a major source of secondary dust explosions. 

Also, layers of dust on items of equipment act as insulators which can cause an item of equipment to overheat, and this can lead to smouldering of the dust layer in contact with the surface of the equipment. Smouldering dust layers are potential ignition sources of explosive dust atmosphere.

BS EN 60079-10-2 defines three levels of housekeeping as follows.

• Good: Dust layers are kept to negligible thickness or are non-existent of the grade of release.  In this case, the risk of the occurrence of explosive dust clouds from layers and the risk of fires has been removed.

• Fair: Dust layers are not negligible but are short-lived (less than one shift).  The dust is removed before any fire can start.

• Poor: Dust layers are not negligible and persist for more than one shift.  The risk may be significant, and this should be controlled by selecting equipment according to BS EN 60079-14.

Leaks from equipment should not be left to persist.  Instead, these should be cleaned up as soon as possible using a suitable vacuum cleaner (and not by sweeping or blown off with compressed air). 

If vacuum cleaners are to be used within a Zone 22, they should be ATEX compliant to Ex II 3D.  If the vacuum cleaners are to be used within non-hazardous areas, it is important that the vacuum cleaners have multi-stage filtration upstream of the motor (at least two individual layers of filtration before the motor).  This minimises the risk of dust entering the motor if one of the filters were to fail. 

Furthermore, it is advisable that only vacuum cleaners that are of a metal construction are used, as these will provide some form of containment in the event of a fire in the collection bag.

Ignition Source Control – Not just ATEX Equipment

Thirteen ignition categories need to be considered and are listed in BS EN 1127-1. They are summarised as follows:

1. Hot surfaces.
2. Flames and hot gases (including hot particles).
3. Mechanically generated sparks.
4. Unsuitable or malfunctioning electrical apparatus.
5. Stray electrical currents, cathodic corrosion protection.
6. Static electricity.
7. Lightning.
8. Radio frequency (RF) electromagnetic waves.
9. Visible light electromagnetic waves.
10. Ionising radiation.
11. Ultrasonics.
12. Adiabatic compression and shock waves.
13. Exothermic reactions, including self-ignition of dusts.

An ignition source assessment is governed by the following two considerations:

• The probability that the ignition source is present. This depends on the severity of the hazardous area (whether it is a Zone 20, 21, or 22).
• The probability that the identified ignition source is effective enough to ignite the materials. The answer to this question depends on two sub-aspects, these are:
  • The strength of the ignition source, which is either indicated by the temperature produced or an amount of energy dissipated. This will be judged on a case-by-case basis for each identified ignition source. 
  • The ignition sensitivity of the materials represented by the minimum ignition energy (MIE).

Figure 3: Two examples of ignition sources

Explosion Protection

The final backstop in comprehensive dust hazard management when trying to achieve an acceptable basis of safety in relation to explosive dust atmospheres is explosion protection. If risk cannot be adequately controlled by means of explosion prevention, the detrimental effects should be mitigated by one or more of the following:

1. Explosion relief arrangements, or
2. Explosion suppression, or
3. Containment

We may also seek to remove employees from the hazard range entirely, or as far as is practicably possible. This is required even if an explosion protection system is deployed. Explosion protection systems are not inherently safe and, especially in the case of venting, will present external hazards.

Furthermore, such systems are not infallible. Whilst a sufficient level of reliability will be designed into the system, it is always best to keep operators away from areas where there is an explosion hazard.

For any explosion protection system applied, it must be suitably designed and certified in accordance with relevant standards. The explosion risk assessment should demonstrate that this is the case.

When explosion protection is deployed, we must also ensure that systems are designed to prevent the propagation of fires and explosions up or down stream. When an explosion propagates from one vessel to another, pressure piling and flame jet ignition can occur, leading to a far more severe explosion in the second vessel. Isolation devices/systems include:

• Extinguishing barriers
• Rapid-action valves
• Rotary valves / double butterfly valves
• Chokes (powder barrier) e.g., heap beneath silo, screw conveyor with baffle plate
• Flap valves

When implementing an explosion isolation system (much the same as for the primary explosion protection system), it must be suitably designed and certified in accordance with relevant standards.

Organisational Measures to Ensure Everything We’ve Done Stays in Place

Applying the technical measures required by DSEAR is just one half of effective dust hazard management and compliance, and arguably the easiest half to implement. An ATEX-certified item of equipment only remains ATEX-certified so long as it is used, inspected and maintained correctly.

A static electricity control system will only work so long as it is used, inspected and maintained correctly. A chemical suppression explosion protection system can only be expected to work providing that the same as above is applied.

Failure to uphold these elements will rapidly undo a basis of safety for managing fire and explosion risks. It is because of this that organisational measures and process safety management underpin fire and explosion safety and are frequently mentioned in both the DSEAR approved code of practice as well as the ATEX non-binding guide.

This includes, training, competency management, contractor management, planned preventative maintenance, control of spares, management of change and permit to work systems. Getting these elements right brings a DSEAR or ATEX basis of safety to life.

FAQs: Regulatory Compliance in Dust Hazard Management

What is the purpose of ATEX and DSEAR regulations?
They aim to protect people from fire and explosion risks due to dangerous substances by requiring assessment and control of dust hazards in the workplace

How do I determine if a material is a dust explosion risk?
Assess properties like particle size dispersibility minimum ignition energy and ignition temperature through testing or literature

What is hazardous area classification and why does it matter?
It categorises areas by the likelihood of explosive atmospheres forming so that appropriate controls and certified equipment can be used

What are the three levels of housekeeping under BS EN 60079-10-2?
Good where dust is negligible fair where dust is removed within a shift and poor where dust accumulates beyond one shift

What are the 13 ignition sources to consider?
They include hot surfaces mechanical sparks static electricity electrical faults lightning electromagnetic waves and more

Do I only need to worry about ATEX-certified equipment?
No ignition sources extend beyond equipment and include static electricity and operator activity which must also be assessed and controlled

What is explosion protection and when is it needed?
If explosion risk cannot be eliminated protection systems like venting suppression or containment must be used to mitigate effects

How do I prevent explosion propagation between vessels?
Use explosion isolation devices such as rapid-action valves flap valves rotary valves or extinguishing barriers to stop flame travel

What organisational controls are needed for compliance?
Training competency management maintenance change control and permit systems are critical to keep safety measures effective over time

Can I rely on ATEX equipment alone for compliance?
No certified equipment must be used maintained and inspected correctly within a wider safety management system to remain effective