Over 70% of industrial dust explosions originate during powder addition to liquids—understanding ATEX zones and certified mixing equipment is essential to prevent accidents and costly downtime.
Key Takeaways
- What Are ATEX Zones? ATEX zones classify hazardous areas by likelihood of explosive atmospheres, guiding safe mixer selection and operational precautions.
- How Can Dust-Free Induction Reduce Risk? Ystral TDS and Conti TDS mixers incorporate powders below liquid surfaces, eliminating airborne dust and minimizing explosion hazards.
- Do All Motors Guarantee Compliance? Simply using ATEX-certified motors or gearboxes is not enough; the entire system—including valves, seals, and instrumentation—must be compliant.
Introduction
ATEX mixers are essential in industrial environments where explosive atmospheres may occur due to flammable vapours, combustible dusts, or hybrid mixtures. For engineers, maintenance professionals, and manufacturing managers, understanding ATEX compliance, safe mixer selection, and process-safe powder addition is critical. This guide provides a comprehensive overview of ATEX regulations, hazards, mixer technologies, certification, and operational best practices, equipping technical staff to make informed decisions for hazardous area mixing.
Enhance your understanding of the risks of combustible dust and powder handling
ATEX Zones and Risk Classification in Mixing Operations
ATEX (from ATmosphères EXplosibles) refers to European directives governing equipment and workplaces where explosive atmospheres may occur. In mixing and powder-handling processes, these risks most commonly arise from flammable liquids, vapours, combustible dusts, or a combination of both.
Read our article on Atex basics and zoning and our guide on powder handling.
ATEX is not just about motors or electrics. In reality, the mixing process itself—how powders are added, how liquids circulate, and how air is displaced—often determines whether an explosive atmosphere exists in the first place.
How ATEX Zones Are Defined
Hazardous areas are classified based on how often and for how long an explosive atmosphere is present.
Gas and Vapour Zones
- Zone 0 – Explosive atmosphere present continuously or for long periods
- Zone 1 – Likely to occur during normal operation
- Zone 2 – Unlikely and, if it occurs, only for a short time
Dust Zones
- Zone 20 – Combustible dust present continuously or frequently
- Zone 21 – Dust likely during normal operation
- Zone 22 – Dust unlikely and short-lived
These zone classifications directly determine:
- Which ATEX equipment category is required
- What design features a mixer must have
- Whether additional procedural or organisational controls are needed
In practice, poorly controlled powder addition can turn an otherwise low-risk process into a Zone 20 or Zone 21 environment, dramatically increasing equipment cost and compliance burden.
Explore our ATEX-certified mixing solutions designed for gas and dust zones across food, chemical, pharmaceutical, and FMCG manufacturing.
Potential vs Actual Explosive Atmospheres in Mixing
Not every hazardous area is permanently dangerous. A potentially explosive atmosphere only becomes an actual explosive atmosphere when specific conditions occur at the same time. This distinction is critical in mixing operations, where risks often arise during short but repeatable moments, such as powder tipping, bag emptying, or high-shear dispersion.
The Explosion Pentagon Explained
An explosion can only occur when all five elements of the explosion pentagon are present simultaneously:
- Oxidant – typically oxygen in air
- Fuel – flammable gases, vapours, or combustible dusts
- Ignition source – sparks, hot surfaces, friction, or static electricity
- Dispersion – fuel suspended in air at the right concentration
- Confinement – a vessel, pipe, or enclosure allowing pressure build-up
Mixing processes frequently create perfect conditions for dispersion and confinement, particularly inside tanks, mixers, and transfer lines.
Why Mixing Is High Risk
- Powders flowing from bags or hoppers can generate static charge
- Dust clouds may form above liquid surfaces
- Flammable vapours can accumulate in poorly ventilated vessels
- Even non-combustible powders can become hazardous in hybrid mixtures when flammable vapours are present
This is why ATEX compliance cannot be achieved by fitting an ATEX-rated motor alone. The entire mixing system—including seals, shafts, valves, powder addition method, and control philosophy—must be assessed.
Reducing Risk at the Source
The most effective ATEX strategy is not containment, but prevention:
- Eliminating dust clouds
- Preventing vapour release
- Removing ignition sources before they become relevant
Technologies such as the Conti TDS and TDS Induction Mixer induct powder below the liquid surface significantly reduce the likelihood of forming an explosive atmosphere at all.
Learn more about combustible dust hazards and powder handling here.
Common Hazards in ATEX Mixing
Mixing in hazardous areas introduces several risks beyond the mere presence of flammable substances. Key hazards include:
- Flammable vapours and combustible dusts: Organic powders, alcohols, solvents, and hybrid mixtures
- Aerosol mists: Spray processes and atomisation creating fine flammable clouds
- Sparks, friction, and static electricity: From mechanical seals, rotating shafts, valves, and other moving parts
- Poor ventilation and inadequate containment: Allowing gases or dust to accumulate to hazardous levels
- Unsafe material selection: Using incompatible metals or plastics that can generate static or friction
Why simple motor or gearbox compliance isn’t enough:
Even ATEX-rated motors and gearboxes cannot guarantee full system safety. Static build-up, friction on mechanical seals, or dust accumulation can still trigger ignition. Comprehensive system design, grounding, and dust-free powder induction methods are essential.
Learn how our mixers and induction systems mitigate these risks in hazardous areas.
Hybrid Mixtures and ATEX Risks
Hybrid mixtures occur when powders are combined with flammable liquids or vapours during industrial mixing processes. Even powders considered non-combustible on their own can become hazardous when suspended in a flammable atmosphere, creating a hybrid explosive environment.
How Hybrid Mixtures Form
- Powder addition to liquids: Organic powders (e.g., starch, sugar, cellulose) added to flammable liquids like ethanol, solvents, or oils can create a combustible dust-liquid interface.
- Evaporation of flammable liquids: As volatile liquids evaporate, the vapour may mix with airborne powders, creating an ignitable cloud above the tank.
- Spray or aerosol generation: Mixing processes that produce fine droplets can combine with powders to increase the explosion risk.
Key Hazards
- Ignition sensitivity: Hybrid mixtures can ignite with lower energy sources than pure powders or pure vapours.
- Electrical discharge: Flowing powders can generate static charges, which may ignite vapours in hybrid environments.
- Confined explosions: Enclosed tanks or pipes can amplify the effects of a hybrid mixture ignition.
Mitigation Strategies
- Dust-free induction systems: Using mixers like the Ystral TDS Induction Mixer ensures powders are incorporated below the liquid surface, preventing dust clouds and reducing hybrid explosion risk.
- Controlled addition rates: Limiting how quickly powders are added to liquids reduces the formation of critical hybrid concentrations.
- Proper grounding and earthing: All conductive parts, including hoppers and valves, should be grounded to prevent static sparks.
- Process monitoring: Temperature, humidity, and vapor concentration should be continuously monitored in areas handling hybrid mixtures.
Protect your facility from hybrid mixture hazards by contacting our experts to implement dust-free ATEX-compliant mixing systems.
ATEX Zone Reduction Strategies: Using Ystral for Dust-Free Mixing
Reducing ATEX zones not only lowers the risk of explosions but can also significantly reduce equipment costs and simplify compliance. A key strategy in achieving this is to eliminate airborne dust during powder addition. Ystral’s Conti TDS and TDS Induction Mixers are specifically designed to handle this challenge.
How Ystral TDS Systems Improve Safety
- Dust-Free Powder Induction: Powders are incorporated directly under the liquid surface, preventing dust clouds and eliminating the critical dust-air mixture that can lead to explosions.
- Vertical Circulation Mixing: The mixer ensures homogeneous mixing by circulating contents vertically, avoiding the horizontal rotation that can trap air and generate aerosols.
- Hybrid Powder-Liquid Safety: Even non-combustible powders can form hazardous atmospheres when mixed with flammable liquids or vapours. The TDS system eliminates this risk by controlling the induction process.
- Electrostatic Risk Reduction: Flowing powders can create static charges that ignite dust-air mixtures. Ystral’s design safely manages powder flow and prevents sparks from valves or equipment.
- Flexible Installation: Conti-TDS can be installed externally and recirculate liquids from multiple tanks, working with high viscosities, different batch sizes, and variable liquid levels.
- Full Certification: Ystral systems are certified according to relevant dust and gas explosion directives and available with various ATEX classifications, IEC Ex, and NEC certifications.
Why Conventional Hoods Aren’t Enough
Stainless steel or noise-insulated motor covers cannot prevent ignition risks from heat build-up. Internal temperatures can exceed 60–80°C, voiding ATEX certification. Ystral systems overcome this with active, temperature-controlled ventilation, ensuring internal temperatures remain below critical limits.
Protect your facility and simplify compliance by contacting us today to implement Ystral dust-free mixing solutions in your ATEX zones.
Conclusion
ATEX compliance in mixing operations is critical for safety and regulatory adherence. Understanding zone classifications, potential vs actual explosive atmospheres, and implementing dust-free induction systems like Ystral TDS ensures risk reduction, equipment longevity, and operational efficiency. Selecting complete ATEX-certified systems—not just individual components—protects people, processes, and productivity.
Frequently Asked Questions
What does ATEX mean?
ATEX refers to European directives for equipment used in explosive atmospheres, ensuring safety against risks from flammable gases, vapours, or combustible dust.
What is a DSEAR assessment?
A DSEAR (Dangerous Substances and Explosive Atmospheres Regulations) assessment evaluates workplace risks from explosive substances and specifies control measures for safe operations.
What is meant by ATEX ‘Zones’?
ATEX zones classify areas by the likelihood and duration of explosive atmospheres, guiding equipment selection and operational safety practices.
Why is it important to operate with ATEX / UKEX certified equipment?
Certified equipment is designed to prevent ignition sources, reducing the risk of explosions and ensuring compliance with safety legislation.
Does using a certified ATEX motor or gearbox alone comply with regulations?
No. Entire systems—including mixers, seals, valves, and instrumentation—must meet ATEX standards; using only a certified motor does not guarantee compliance.
What does ‘flameproof’ or ‘explosion-proof’ mean?
It refers to equipment designed to contain and prevent ignition of explosive gases or dust, even under internal fault conditions.
What is an Ex ‘e’ enclosure?
Ex ‘e’ denotes an increased safety enclosure, designed to prevent sparks or hot surfaces inside from igniting external explosive atmospheres.
For ATEX/DSEAR, is it better to use air-driven or electric motors?
Air-driven mixers often reduce ignition risks, but the overall system must be certified; electric motors can be used if fully ATEX-rated and installed correctly.
Does “air-driven” always mean ATEX compliant?
Not necessarily. Air-driven equipment must still meet ATEX standards; certification applies to the complete system, not just the power source.
Which type of shaft seal do I need for ATEX?
Seals must be designed to prevent leakage and minimize ignition risks; TDS mixers use ATEX-compliant mechanical seals suitable for dust and liquid applications.
Recommended Websites
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Health and Safety Executive (HSE)
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Detailed guidance on DSEAR, ATEX zones, and risk management in industrial environments.
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European Commission – Equipment for potentially explosive atmospheres (ATEX)
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Ystral GmbH – Technical and case studies on TDS mixers