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Simplifying Complexity.
Delivering Safety.
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Pre-start ventilation systems for large Ex e & Ex n electric motors & generators

In some cases, high-voltage Ex e and Ex n motors installed in hazardous areas require “special measures” to be implemented prior to start-up, to reduce risks of ignition caused by air gap sparking.  These measures typically include pre-start ventilation the motor casing with instrument air for a specified time to eliminate any build-up of hazardous gases or vapours.

With more than 1,300 pre-start ventilation systems supplied for large electric motors and generators, Expo is the world’s most experienced designer and manufacturer.

Use the table below to choose a system suitable for your application

Pre-start ventilation gas flowrate /
Expo system size
–20°C to +60°C
-50°C to +60°C
Up to 1500 Nl/min
Up to 6000 Nl/min
Up to 14,000 Nl/min
Hazardous area motor with Expo pre-ventilation system

Special motor pre-start ventilation systems

Expo can design and build custom motor pre-start ventilation systems, for instance for very large motors where high flow rates are required Please call +44 (0) 20 8398 8011 to speak to one of our purge and pressurization experts or contact us.

Range Overview

Expo’s pre-start ventilation control units will enable your motors & generators to meet:

  • ATEX or IECEx requirements for Zone 1, Zone 2
  • NPFA requirements for Class I Div 1 & Div 2, Class I Zone 1 & Zone 2


Typical system features:

  • Airflow rates for all motor sizes from 500 l/min to 14,000 l/min.
  • Standard ambient temperature range -20°C to +60°C. Low temperature option to -50°C for extreme locations.
  • Certification for ATEX, IECEx, NFPA to meet most project requirements
  • Local start is standard, with remote start interface for motor control centres or distributed control systems
  • Purge timer: accurate and repeatable purge times up to 99 minutes. IS (Intrinsically Safe) Battery or electro-pneumatic power supply (EPPS) options
  • 316L stainless steel enclosure for long service life in harsh conditions
  • Ex e junction box & terminals for system status & alarms. Optional Ex i, Ex d junction boxes.
  • Guaranteed performance and site acceptance for reduced project timescales
  • Optional extended running to prevent delays where process conditions cause motor trips after start-up.


  • Proven solutions for Ex e & Ex n machines
  • Largest, most global installed base
  • Systems for very large machines
  • Options for harsh environments

Configure your product

Use our product configurator tool to build a system to your exact specification.