In industries handling flammable gases, vapours, solvents, or combustible dust, ventilation equipment must be selected with more than airflow and pressure in mind. A fan installed in a hazardous area can itself become an ignition source if it is not correctly specified.

This is where ATEX and IECEx-rated ventilation equipment becomes important.

What Is Explosion-Proof Ventilation?

Explosion-proof ventilation is designed for areas where an explosive atmosphere may occur. The objective is to maintain safe contaminant concentrations while reducing the possibility of the ventilation equipment becoming an ignition source.

These systems are commonly required in:

• Chemical and petrochemical plants
• Paint and coating facilities
• Pharmaceutical plants
• Oil and gas facilities
• Solvent handling areas
• Battery and chemical processing
• Industries handling combustible dust.

ATEX vs IECEx

ATEX is the European regulatory framework for equipment used in potentially explosive atmospheres.

IECEx is an international certification system based on IEC standards for equipment used in explosive atmospheres.

The important point for plant engineers is that certification should be selected according to the hazardous-area classification, process conditions, and project requirements. An ATEX or IECEx label alone does not mean a fan is suitable for every hazardous application.

Understanding Hazardous Area Zones

For gases and vapours:

• Zone 0: Explosive atmosphere is present continuously or for long periods.
• Zone 1: Explosive atmosphere is likely during normal operation.
• Zone 2: Explosive atmosphere is unlikely during normal operation but may occur temporarily.

For combustible dust, the corresponding classifications are Zone 20, Zone 21, and Zone 22.

The fan and associated equipment must be suitable for the specific zone in which they are installed.

Why an Explosion-Proof Motor Is Not Enough

One common mistake is to specify an explosion-proof motor and assume the complete fan is therefore suitable for a hazardous area.

The fan assembly must also be considered for potential ignition sources such as:

• Impeller-to-casing contact
• Mechanical friction
• Bearing overheating
• Static electricity
• Hot surfaces
• Incorrect clearances
• Material buildup

Fan construction, impeller material, clearances, bearings, motor arrangement, earthing, and associated electrical equipment all require consideration.

Temperature Class Matters

The temperature class indicates the maximum surface temperature that the equipment can reach.

For gas and vapour applications, common classes range from T1 to T6.

The selected equipment must have a temperature classification appropriate for the hazardous substance being handled. Selecting the correct zone but ignoring temperature class can result in an unsuitable equipment specification.

Key Parameters for Selecting a Hazardous-Area Fan

Before selecting the fan, establish:

1. Hazardous substance –  gas, vapour, mist, or combustible dust
2. Hazardous zone – Zone 0, 1, 2 or Zone 20, 21, 22
3. Gas or dust group
4. Temperature class
5. Required airflow
6. System static pressure
7. Operating temperature
8. Fan and motor construction
9. Required ATEX/IECEx certification
10. Control and electrical equipment requirements

The fan should be selected based on the combination of hazard classification and actual operating duty, not certification alone.

Common Applications

Explosion-protected ventilation is used for:

• Solvent and chemical handling
• Paint booths and coating lines
• Pharmaceutical processes
• Oil and gas facilities
• Chemical storage areas
• Combustible dust extraction
• Battery and specialty chemical manufacturing.

Common Specification Mistakes

Avoid these common errors:

• Specifying only an “explosion-proof fan”
  The RFQ should clearly state the hazardous-area classification and operating conditions.
• Selecting based only on CFM
  The fan must deliver the required airflow at the actual system static pressure.
• Ignoring the fan assembly
  The motor certification does not automatically address mechanical ignition risks within the fan.
• Using standard accessories
  VFDs, sensors, junction boxes, actuators, and other electrical components may also need hazardous-area suitability.
• Ignoring maintenance
  Impeller balance, bearing condition, clearances, grounding, and material buildup should be checked periodically.

Final Takeaway

Aarco Engineering Projects can support the selection and engineering of industrial ventilation systems for demanding process environments.

For hazardous-area applications, we can evaluate the airflow, static pressure, process temperature, hazardous material, zone classification, fan construction, and motor requirements to develop a ventilation solution suited to the operating conditions.

Choosing a hazardous-area fan is not simply about purchasing an explosion-proof motor.

The correct selection requires matching:

Hazard → Zone → Group → Temperature Class → Fan Duty → Construction → Motor → Controls

Getting these parameters right is essential for reliable and safe industrial ventilation in potentially explosive environments.