Hazardous Area
Experts answer four critical questions related to protection in dangerous locations.

When it comes to using equipment in hazardous classified areas that is manufactured in other countries, what are the rules? What certifications are necessary? And how do you tell if equipment is safe for your application? To learn more about this topic, Eaton field application specialist Robert Potter and Dupont electrical engineering consultant Ricard Holub provided some answers to common questions.

1. What are the primary equipment safety challenges in hazardous areas?

Hazardous classified locations contain flammable gas, liquids or vapors, combustible dusts or easily ignitable fiber and flyings. When one of these is combined with an oxidizer and ignition source, the result may be an explosion or fire.

In North America, equipment meeting relevant hazardous area location certifications first must meet ordinary location requirements. These ordinary standards include but are not limited to: Underwriters’ Laboratories (UL) 94-v0 standard for flammability, UL 489 for molded case circuit breakers, UL 50 and National Electrical Manufacturers Association (NEMA) 250 standards for electrical enclosures and UL 1581 standard for electrical wires, cables and flexible cords.

There is a common shortfall with hazardous area solutions overseas; they may not be tested to the general American ordinary location standards for suitability. In contrast, North American products applied in hazardous locations classified areas must first meet the requirements of ordinary locations before approval for hazardous areas may be achieved.

When no other product is available, and organizations need to use technology from outside of North America, there are the National Electrical Code (NEC) and Occupational Safety and Health Administration (OSHA) exceptions. It is essential to understand there is tremendous liability in using those technologies if equipment is not certified to North American standards.

2. How is equipment certified for safe use in hazardous areas?

The zone method has become an accepted practice worldwide for classifying hazardous classified locations. The International Electrotechnical Commission system (IECEx system) for certification to standards relating to equipment for use in explosive atmospheres lists 62 countries that are full members and an additional 26 as associate members. Many countries have their own directives and certification requirements for equipment approvals within their borders. The zone method dates back to 1996 and was first introduced by the NEC and National Fire Protection Association (NFPA) with Article 505. It allows for parallel classification in the traditional NEC Article 500 division system.

In this division system, zone terminology was used as the international system for classification of hazardous locations containing flammable gases, liquids or vapors, combustible dust or ignitable flyings, which divided classified areas into three segments: Zone 0, Zone 1 or Zone 2 for gases/ vapors as well as Zone 20, Zone 21 and Zone 22 for combustible dust and ignitable flyings.

Today, zone-rated equipment still requires certification of ordinary location requirements in the U.S. The AEx marking, developed by the American National Standards Institute (ANSI) and International Society of Automation (ISA), ensures that zone equipment conforms with hazardous location requirements and the ordinary location American safety standards. As such, the AEx symbol is a critical marking requirement within the zone material nomenclature.

The Authority Having Jurisdiction (AHJ) and qualified testing labs have an essential role. The AHJ can approve equipment when there is sufficient safety data. Further, if equipment is listed by a qualified lab, then the internals of the equipment do not need to be inspected, except to look for problems, changes or damage.

3. What if an AEx-Zone or division-certified technology is not available?

The NEC Article 500.8(A) addresses this possibility. It indicates that the suitability of equipment is determined by one of the following: equipment listing, evidence of equipment evaluation from a qualified testing lab or AHJ or evidence acceptable to the AHJ like a manufacturer’s self-evaluation or owner’s engineering judgment.

A manufacturer’s self-certification and owner’s engineering judgment must be carefully reviewed and only be considered when the decision-maker is fully confident that ordinary safety standards have been achieved. This evidence must also be accepted by the AHJ.

OSHA provides additional guidance and requirements for product allowance. OSHA 29 CFR 1910.399 defines acceptable equipment as:

  • if it is determined safe by a nationally recognized testing lab
  • if it is inspected by another federal agency or by a state, municipal or
  • other local authority responsible for enforcing occupational safety provisions of the NEC and found in compliance with the NEC
  • if the equipment is determined to be safe for its intended use by its manufacturer based on test data that the employer keeps and can provide for inspection

4. What should users consider when purchasing electrical equipment for hazardous areas?

The OSHA and NEC allowances permit for a product to be approved for installation without third-party testing by a nationally recognized testing lab (NRTL); OSHA lists 19 NRTLs on their website, including UL, CSA and ETL-Intertek.

However, both the OSHA and NEC language indicate that the general rule
is equipment should be tested and listed by a NRTL—unless these avenues have been exhausted.

When thinking about electrical equipment without testing by a NRTL, it is important to consider:

  • Does the state or municipality where equipment is being installed have requirements only allowing for the installation of third-party evaluated equipment?
  • Does the end user facility have requirements only allowing for installation of third-party NRTL evaluated equipment?
  • Who is shouldering the liability for the owner’s engineering judgment or self-evaluated equipment for suitability of ordinary and hazardous-area locations?

Facilities using the NEC Articles 505 and 506 Zone classification of hazardous location classified areas are governed by the approval requirements outlined in the NEC articles for the wiring methods and equipment certification.

When zone method rated equipment includes the AEx marking, it means the equipment is certified to the American standards per NEC Article 505.9 (C) and Article 506.9 (C). That AEx marking ensures the zone equipment conforms with both hazardous location requirements and general safety American standards for ordinary locations. These certifications give users confidence and trust in the equipment they are applying.