Purge and Pressurization Enclosures

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Purge and Pressurization Enclosures

Expo’s complete Purge and Pressurized enclosures enable you to install uncertified electrical equipment in hazardous areas. OurPurge Wizard identifies the appropriate purge and pressurization unit for your enclosure.

North America

Expo Purging & Pressurization Systems have UL Listing for US hazardous locations and cUL listing for Canadian Zones.

We often assist customers obtain hazardous location approval from their preferred inspection authority.

Europe Brazil Rest of World

If Expo provides the enclosure and the purging system, we certify it to IECEx or ATEX standards. Our certificates let us deliver a complete range of custom solutions.

If Expo provides a purging system which you attach to your enclosure, a Notified Body must certify it. We regularly work with your local Notified Body to obtain certification.

Benefits of Expo’s Purge and Pressurised Enclosure

Quick Access: Easily open purged cabinets for maintenance in hazardous areas;

+ Zone 1 or Class I Div 1: When the door opens and the internal air-pressure falls,  power automatically switches off. When the door closes, after the required number of purge cycles the enclosure  automatically powers-up.
+ Zone 2 or Class I Div 2: When the door opens, a low-pressure alarm sounds. However, the equipment  operates for a time you set, based on local risks.

Controls: We often add:

  • Windows: for viewing displays;
  • HMI units either directly, if they support pressurization, or into inset housings, if separately approved;
  • Operator interfaces: push buttons, lamps, switches, and annunciators.  We must use certified components since they sit outside the enclosure.

Heating & cooling: Our enclosures often include local heating or cooling:

  • Electric heating;
  • Thermostats;
  • Fan-driven heat exchangers;
  • Vortex coolers.

Wheels: Move certified electrical equipment between points of use in hazardous areas.

  • Multiple hazardous areas can share a single piece of equipment;
  • E.g. filter cleaning systems in pharmaceutical plants.

 Custom Enclosure

Why Use Expo Purge and Pressurized Enclosures

Expensive alternatives to Expo’s purge and pressurized enclosures include:-

Explosion-Proof boxes(Ex d): can withstand an internal explosion, and prevent any internal ignition reaching surrounding gas or vapour. However, these are heavy, solid metal boxes, generally castings, or specially welded/fabricated. Hence:

  • Access, e.g. for maintenance, is time-consuming because multiple bolts or thread engagements secure the lid;
  • Design changes are expensive, because any modification, e.g. local drilling, is forbidden;
  • Extracting internally generated heat is expensive and difficult;
  • Large boxes are disproportionately expensive;
  • Boxes are approved for specific internal equipment layouts.

Increased safety enclosures (Ex e):  for equipment that doesn’t arc or spark during normal or fault conditions. The enclosure is insulated to keep surface temperatures below incendive temperatures.  However:

  • Only Ex e approved components can be installed inside the enclosure;
  • No sparking or arcing equipment is permitted;
  • The enclosure’s certificate sets specific conditions & limits.

Purge and Pressurization is cost-effective:

  • A single Purge and Pressurization unit often purges multiple enclosures in series;
  • When equipment or requirements change, Purged and Pressurized units are easy to re-configure or upgrade;
  • A single Purge and Pressurization unit often replaces multiple explosion-proof boxes and interlinking conduit.

Expo’s Purge & Pressurization Capabilities

Expo has designed hundreds of custom purge and pressurized enclosures. For purge and pressurization technology, we believe we are:

  • World experts – we contributed to the world’s first Ex p standard;
  • The market’s most experienced supplier – 60 years of service;
  • Global market leader – the first name on everyone’s lips for purge systems.

Typical Enclosure System

How we might work together

Our design will meet your requirements. We’ll provide whatever technical assistance you need.

We manufacture enclosures in:

  • 1-off’s, for special designs;
  • Batches for OEM’s. We’ll enable your customers to use your systems safely and easily, with minimal changes to your standard product & applications.

Many customers work with us this way:

  1. You specify the equipment inside your enclosure,  for what environment.
  2. Expo delivers an enclosure design that meets your  specification, and recommends an appropriate purging system from our extensive range.
  3. We agree on a Bill of Materials, General Arrangement and Certification route.
  4. Expo manufactures your enclosure and fits our purging system.
  5. Expo either fits out the enclosure, or more commonly,  ships the enclosure to you.  You fit  your equipment inside.
  6. Either Expo or a Notified Body inspects the enclosure and issues a compliance certificate.

 Multiple Enclosures

Expo Purge and Pressurization Customers






Rockwell Automation

North American Certificates

Expo Purge and Pressurization enclosure hazardous area certificates:

  • SmartPurge II Control System, USA (FM Approval)
  • SmartPurge II Control System, Canada (FM Approval)
  • MiniPurge Control Unit Types X, Y, Z (UL Listing)
  • MiniPurge Control Unit Types X, Y, Z (FM Approval)
  • Solenoid Operator Type J & K (FM Approval)
  • Electronic Timer – Intrinsically Safe, USA (FM Approval)
  • Electronic Timer – Intrinsically Safe, Canada (FM Approval)


Expo Purge and Pressurization enclosure hazardous area certificates:

  • Pressurized Enclosures Zone 1
  • Pressurized Enclosures Zone 2
  • Dust Protected Enclosures Zone 1
  • Dust Protected Enclosures Zone 2
  • PE2(E) & PE3(E) Component Certified Enclosures


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