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Simplifying Complexity. Delivering Safety.
Simplifying Complexity.
Delivering Safety.

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.

Download our brochure to find out more.

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.