ATEX

ATEX is the European Union framework for protecting people and equipment where potentially explosive atmospheres may occur.

The name comes from the French term ATmosphères EXplosibles.

ATEX is particularly important in industrial dust collection because combustible materials such as wood dust, plastic powder, food powder, chemical powder, coal dust, and some metal dusts can form explosive mixtures when dispersed in air under suitable conditions.

ATEX should not be understood as a single certificate or as simply installing an explosion-proof motor.

For a combustible-dust application, ATEX compliance may involve hazard assessment, hazardous-area classification, equipment category, ignition-source control, explosion protection, marking, technical documentation, and conformity assessment.

What Are the Two Main ATEX Directives?

Two EU directives are particularly important when discussing ATEX.

Directive 2014/34/EU — Equipment and Protective Systems

Directive 2014/34/EU primarily applies to manufacturers and products intended for use in potentially explosive atmospheres.

It covers equipment and protective systems, as well as certain safety, controlling, and regulating devices that are important for explosion safety.

Depending on the product and equipment category, the manufacturer may need to:

• Assess explosion hazards associated with the equipment
• Prepare technical documentation
• Complete the applicable conformity assessment
• Issue an EU Declaration of Conformity
• Apply CE marking
• Apply the specific explosion-protection marking
• Identify the equipment group and category
• Provide instructions for safe installation and use

For a dust collector manufacturer supplying equipment to the EU, this is the main ATEX product directive.

Directive 1999/92/EC — Workplace Protection

Directive 1999/92/EC focuses on the workplace and the protection of workers who may be exposed to explosive atmospheres.

It requires the employer to assess explosion risks and classify hazardous places according to how frequently and for how long an explosive atmosphere may be present.

For combustible dust, the relevant zones are:

• Zone 20
• Zone 21
• Zone 22

A simple way to distinguish the two directives is:

1999/92/EC → Where can an explosive atmosphere occur?

2014/34/EU → What level of protection must equipment provide for its intended use?

What Is an Explosive Atmosphere?

Under ATEX, an explosive atmosphere is a mixture with air, under atmospheric conditions, of flammable substances in the form of gas, vapour, mist, or dust in which combustion spreads through the unburned mixture after ignition.

For industrial dust applications, the basic concern is:

Combustible Dust + Air + Suitable Concentration + Ignition Source

Not every dusty process automatically creates an explosive atmosphere.

Actual explosion risk depends on factors such as:

• Dust material
• Particle size
• Dust concentration
• Moisture
• Kst
• Pmax
• Minimum Ignition Energy (MIE)
• Minimum Ignition Temperature (MIT)
• Process temperature
• Operating conditions

A proper combustible-dust assessment should therefore use actual process and dust data rather than relying only on the material name.

What Are Zones 20, 21 and 22?

ATEX workplace rules classify combustible-dust hazardous areas according to the frequency and duration of an explosive dust atmosphere.

Zone 20

Zone 20 is a place where an explosive atmosphere in the form of a combustible dust cloud is present:

• Continuously
• For long periods
• Or frequently

Some equipment interiors may meet this definition depending on the process, but not every dust collector should automatically be classified the same way.

Zone 21

Zone 21 is a place where an explosive dust atmosphere is likely to occur occasionally during normal operation.

Zone 22

Zone 22 is a place where an explosive dust atmosphere is not likely to occur during normal operation, but if it does occur, it will normally persist only for a short time.

Does a Higher Zone Number Mean the Dust Is Less Dangerous?

No.

Zone classification does not describe how severe or energetic the dust explosion itself would be.

It mainly describes how frequently and for how long an explosive atmosphere is expected to occur.

For example, the same combustible powder could be associated with different zone classifications at different locations within one factory.

Inside process equipment, a combustible dust cloud may occur frequently.

Outside the equipment, a dust cloud may occur only during an abnormal or occasional release.

Dust properties such as Kst, Pmax, MIE, particle size, and moisture are therefore separate from the zone classification, even though both are important to explosion-risk assessment.

Do Dust Layers Matter Under ATEX?

Yes.

Combustible dust does not need to remain suspended continuously to create a hazard.

Dust may accumulate on:

• Floors
• Machinery
• Beams
• Cable trays
• Ductwork
• Structural surfaces
• Equipment housings

Deposited dust can later become airborne again because of vibration, air movement, compressed-air cleaning, or an initial explosion.

ATEX workplace rules specifically require layers, deposits, and heaps of combustible dust to be considered as potential sources capable of forming an explosive atmosphere.

Good housekeeping is therefore part of combustible-dust risk control.

What Are ATEX Equipment Groups?

Directive 2014/34/EU divides equipment into two main groups.

Equipment Group I

Group I applies primarily to underground mines and associated surface installations that may be endangered by firedamp or combustible dust.

Its categories are:

• M1
• M2

Equipment Group II

Group II covers other locations where explosive atmospheres may occur.

Most industrial dust collection applications in facilities such as:

• Woodworking plants
• Food factories
• Chemical plants
• Pharmaceutical facilities
• Metalworking factories
• Powder-processing plants

fall under Equipment Group II.

Group II equipment is divided into:

• Category 1
• Category 2
• Category 3

What Do ATEX Categories 1, 2 and 3 Mean?

The equipment category indicates the required level of protection.

Category 1

Category 1 provides a very high level of protection.

It is intended for areas where explosive atmospheres are present continuously, for long periods, or frequently.

For combustible dust, this category is associated with Zone 20 applications.

Category 2

Category 2 provides a high level of protection.

For dust applications, it is commonly associated with Zone 21.

Equipment in this category must be designed so that ignition of an air/dust mixture is prevented even during certain expected disturbances or equipment faults.

Category 3

Category 3 provides a normal level of protection.

It is intended for areas where explosive atmospheres are unlikely during normal operation or occur only infrequently and for short periods.

For combustible dust, it is commonly associated with Zone 22.

How Do Dust Zones and Equipment Categories Relate?

The ATEX workplace directive provides the following general equipment-selection relationship:

Dust Zone	Suitable Equipment Category
Zone 20	Category 1
Zone 21	Category 1 or 2
Zone 22	Category 1, 2 or 3

The equipment must also be suitable for the relevant type of explosive atmosphere and actual operating conditions.

A typical marking may include:

II 2D

Where:

• II = Equipment Group II
• 2 = Category 2
• D = Dust atmosphere

What Do G and D Mean in ATEX Marking?

For Group II equipment:

• G refers to explosive atmospheres caused by gases, vapours, or mists.
• D refers to explosive atmospheres caused by dust.

Industrial dust collection projects therefore commonly focus on equipment marked for D — Dust applications.

The complete Ex marking may contain additional information related to:

• Protection concept
• Dust group
• Maximum surface temperature
• Equipment Protection Level
• Ambient temperature range
• Specific conditions of use

The complete marking must be evaluated rather than relying only on the presence of an “ATEX” label.

Is CE Marking the Same as ATEX?

No.

CE marking indicates conformity with applicable EU legislation for the product.

ATEX Directive 2014/34/EU may be one of the EU requirements applicable to equipment intended for use in potentially explosive atmospheres.

Therefore:

CE marking alone does not mean that equipment is suitable for an ATEX hazardous area.

Equipment covered by Directive 2014/34/EU must also carry the applicable explosion-protection marking and information required for its intended use.

For example, a standard CE-marked electric motor is not automatically suitable for installation in a Zone 21 dust environment.

Does Every ATEX Product Require Third-Party Certification?

No.

The conformity assessment route depends on the equipment group, category, equipment type, and whether the product is a protective system.

For example:

Category 1

Category 1 equipment requires EU-type examination together with an applicable production conformity procedure involving a Notified Body.

Category 2

For Category 2 electrical equipment and internal combustion engines, EU-type examination and additional conformity procedures are required.

For other Category 2 equipment, Directive 2014/34/EU allows internal production control with the required technical documentation communicated to a Notified Body for retention.

Category 3

Group II Category 3 equipment may use internal production control.

Therefore, the phrase “ATEX certificate” can sometimes oversimplify the actual legal conformity process.

Not every ATEX product follows the same certification route.

What Is an EU-Type Examination Certificate?

EU-type examination is a conformity assessment procedure in which a Notified Body examines the technical design of a product.

When the evaluated type satisfies the applicable requirements of Directive 2014/34/EU, the Notified Body issues an EU-Type Examination Certificate.

However, this certificate is only one part of the applicable conformity process.

Where required, the manufacturer must still complete the relevant production conformity procedure, prepare the required documentation, issue the EU Declaration of Conformity, and apply the required markings.

Is an ATEX Motor Enough for an ATEX Dust Collector?

No.

A dust collection system can contain many components that may affect explosion safety, including:

• Fan
• Motor
• Bearings
• Filter bags or cartridges
• Rotary airlock
• Screw conveyor
• Solenoid valves
• Sensors
• Control devices
• Hopper
• Ductwork
• Explosion vent
• Explosion isolation device

Potential ignition sources are not limited to electrical components.

Mechanical equipment can also create ignition hazards through:

• Friction
• Impact sparks
• Overheated bearings
• Hot surfaces
• Static electricity
• Mechanical failure

Installing an ATEX-rated motor on a conventional dust collector does not automatically make the complete dust collector ATEX compliant.

The entire equipment design and intended operating conditions must be evaluated.

Does Anti-static Filter Media Make a Dust Collector ATEX Compliant?

No.

Anti-static filter media can help dissipate electrostatic charge and reduce one potential ignition mechanism.

However, explosion safety may also require:

• Bonding and grounding
• Hot-surface control
• Mechanical ignition-source control
• Suitable Ex electrical equipment
• Spark or ember control
• Explosion venting
• Explosion suppression
• Explosion isolation
• Safe material discharge
• Process interlocks

Anti-static filter media is therefore one possible part of an ignition-control strategy, not proof of complete ATEX compliance.

Is Explosion Venting the Same as ATEX?

No.

Explosion venting is an explosion-protection technique.

It is designed to relieve pressure if an explosion occurs inside equipment.

ATEX is the broader regulatory framework governing equipment and workplaces exposed to explosion risks.

Depending on the application, a dust collection system may use measures such as:

• Explosion venting
• Flameless venting
• Explosion suppression
• Explosion isolation

The appropriate protection method depends on the dust characteristics, equipment design, installation location, and explosion-risk assessment.

What Is the Basic ATEX Explosion-Safety Strategy?

Directive 2014/34/EU applies the principle of integrated explosion safety.

The basic logic can be summarized in three stages.

1. Prevent Explosive Atmospheres Where Possible

Examples include:

• Reducing dust release
• Containing powder processes
• Improving source capture
• Preventing excessive dust accumulation

2. Prevent Ignition

Potential measures include:

• Bonding and grounding
• Controlling surface temperature
• Preventing mechanical sparks
• Using suitable Ex electrical equipment
• Monitoring overheating
• Controlling sparks and glowing particles

3. Limit the Effects of an Explosion

Where explosion risk cannot be eliminated, protection may involve:

• Explosion venting
• Explosion suppression
• Explosion isolation
• Other suitable protective systems

An effective combustible-dust strategy generally considers all three levels rather than relying on one protective device.

Who Determines the ATEX Zone?

Hazardous-area classification is part of the workplace explosion-risk assessment.

For an industrial project, zone classification should normally be established by the plant operator, employer, or competent explosion-safety professionals based on the actual process.

Factors can include:

• Dust release source
• Release frequency
• Release duration
• Dust properties
• Ventilation
• Equipment enclosure
• Process conditions
• Housekeeping
• Dust accumulation

The employer is also responsible under Directive 1999/92/EC for preparing and maintaining an Explosion Protection Document demonstrating that explosion risks have been assessed and appropriate measures are in place.

A dust collector manufacturer can support equipment selection, but should not simply guess the customer’s hazardous-area classification.

Can the Internal and External ATEX Zones of a Dust Collector Be Different?

Yes.

The dust collector interior and the surrounding installation area can have different hazardous-area classifications.

Inside the collector, combustible dust clouds may occur frequently during normal filtration and cleaning.

Outside the collector, the atmosphere may be different if the equipment is properly sealed and dust is not normally released.

Conversely, if powder regularly leaks during discharge or maintenance, the surrounding area may also require hazardous-area classification.

Therefore:

Internal zone classification and external zone classification should be assessed separately.

It is incorrect to assume that the entire room automatically has the same zone as the collector interior.

ATEX vs. IECEx

ATEX and IECEx are both associated with explosive atmospheres, but they are not the same system.

ATEX

ATEX is part of the European Union legal framework.

It governs the placing of relevant equipment on the EU market and workplace explosion safety.

IECEx

IECEx is an international conformity assessment system based on IEC standards for explosive atmospheres.

One important difference is that IECEx equipment certification uses independent certification through approved IECEx bodies, while ATEX conformity assessment routes vary depending on equipment category and type.

An IECEx certificate does not automatically replace the legal ATEX requirements for equipment placed on the EU market.

Some international projects may request both ATEX and IECEx.

What Information Is Needed for an ATEX Dust Collection System?

Before designing or selecting equipment for a combustible-dust application, important project information may include:

• Dust type
• Particle size
• Dust concentration
• Kst
• Pmax
• Minimum Ignition Energy
• Minimum Ignition Temperature
• Internal zone classification
• External zone classification
• Required equipment category
• Operating temperature
• Airflow
• Static pressure
• Installation location
• Indoor or outdoor installation
• Duct arrangement
• Process operating sequence
• Simultaneously operating equipment
• Applicable EU standards
• Customer explosion-protection requirements

These data can affect decisions involving:

• Fan and motor selection
• Filter media
• Bonding and grounding
• Sensors
• Rotary airlocks
• Explosion venting
• Explosion isolation
• Control logic
• Equipment marking
• Conformity assessment

ATEX should therefore be considered from the beginning of a combustible-dust system design rather than treated as an accessory added after the dust collector has already been selected.