Material Concerns in Explosion-Proof Product Design

Hazardous areas require special attention from specifiers. These are 
areas, as defined in the National Electrical Code, where a combustible 
atmosphere raises a risk of explosion if sparks or open flames or 
present. This risk could be the result of flammable gases, combustible 
vapors, combustible dust or easily ignitable fibers. Hubbell Incorporated

Chuck Ross

Hazardous areas require special attention from specifiers. These are areas, as defined in the National Electrical Code, where a combustible atmosphere raises a risk of explosion if sparks or open flames or present. This risk could be the result of flammable gases, combustible vapors, combustible dust or easily ignitable fibers.

“Explosion-proof” can be easily confused with “intrinsically safe,” another term frequently seen in specifications for hazardous locations. Intrinsically safe products are designed to eliminate all possibility of ignition in dangerous settings. Explosion-proof lighting, enclosures, and other electrical products are, instead, designed to keep any ignition that occurs within the device from spreading.

So, the goal for the designers of explosion-proof offerings isn’t to keep the surrounding, flammable atmosphere out of devices and enclosures. Instead, devices and enclosures are expected to be able to contain any resulting explosion within themselves, without rupturing. The goal is to prevent any kind of ignition within a device from cascading into a much larger explosion in the surrounding area.

Material selection is key to the design of explosion-proof equipment. The use of material that doesn’t contain iron (called “non-ferrous”) significantly reduces the risk of sparks resulting from impact or friction. While cold sparks can still occur, these don’t produce enough heat to ignite flammable gases, dust or fibers. Because they don’t contain iron, these products also are at lower risk of corrosion over time. Metallic, non-sparking options include:

  • Copper-aluminum alloys
  • Stainless steel
  • Silver
  • Aluminum
  • Galvanized steel

Nonmetallic products are even less prone to corrosion than their metallic counterparts. They stand up well to solvents and abrasive cleansers and in wet/humid environments. Plus, they are lighter-weight, where that might be a concern. These materials can include:

  • Fiberglass
  • Polyester
  • Polycarbonate
  • Carbon fiber


Photo courtesy of Hubbell Incorporated

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