Chapter Corner

After the Fire

Posted in: Safety Corner, September/October 2014

If you haven’t been made aware of the fact that electrical equipment exposed to water can be extremely hazardous if re-energized without proper reconditioning or replacement, then you just may also be surprised to hear that a similar message is applicable to electrical equipment exposed to the smoke/soot that may result from burning materials during and after a structure fire. One could argue that a structure fire not only creates an environment that is hazardous to the health of the occupants and first responders, it also has the ability to create a hazardous location caustic to electrical equipment.

As electrical professionals who provide a service to our customers, it is important that we make the right decisions for safety when reviewing electrical equipment located in structures that have experienced fire and/or smoke damage. In addition to your years of experience and training on how to appropriately apply electrical equipment, a resource is available from the National Electrical Manufacturers Association (NEMA) to help make correct decisions with this regard. A recently published NEMA document titled “Evaluating Fire- and Heat-Damaged Electrical Equipment” may be helpful when reviewing electrical equipment in structures that have experienced fire and/or smoke damage. In addition to this NEMA resource, product standards and the National Electrical Code® (NEC) are important during this process as well. The activities that occur after a structure experiences fire, or even just smoke damage, is important for a safe electrical installation. You don’t have to make important decisions alone.

Releasing Chemicals

To understand the caustic environment created by a fire, just look around at the inventory of items in a structure that may ignite and become fuel. There are plastics, wood, various fabrics, glue, electronic equipment, fiberglass, and much more. When materials burn, they experience a chemical change where the elements that make up the materials change state: Some remaining a solid, some taking the form of a liquid, and others take the form of a gas. Materials that burn are considered fuel and when a fuel burns four products of combustion are experienced: Fire gases, flame, heat, and smoke.

The vapors released during a fire have the most ability to extend far beyond the direct location of the fire. This would include fire gases and smoke. Some of the gases released during a fire will rise and others have a tendency to hug the ground, and all of them can be carried by wind or other reasons for air flow. These gases can leave a residue on everything it engulfs. Residue on electrical equipment, especially energized parts, can be quite hazardous.

Structure fires can release large amounts of smoke. Even the smallest of fires, depending on the fuel, can produce a large amount of smoke. Merriam Webster defines smoke as “the gaseous products of burning materials especially of organic origin made visible by the presence of small particles of carbon.”

A fire can release many chemicals toxic if inhaled. They include the following:

  • Carbon monoxide – Produced from organic materials
  • Hydrogen cyanide – Originating from polyurethane, wool, silk, and paper
  • Acrolein (aldehydes) – Result of burning wood, acrylics, cotton, and rubber
  • Nitrogen Dioxide – From cellulose and wood
  • Ammonia – Common due to burning nylon, wood, silk, and polyurethane
  • Hydrogen chloride – Polyvinyl chloride (PVC pipes) and upholstery
  • Hydrogen fluoride – Teflon
  • Hydrogen bromide – Fire retardants
  • Sulfur dioxide – Rubber
  • Isocyanates – Polyurethane, wool, silk, and paper
  • Acrylonitrites – Polyurethane, wool, silk, and paper
  • Hydrogen sulfide – Wool, silk, and rubber
  • Benzene – Petroleum-based plastics
  • Styrene – Polystyrene
  • Phsogene – Polyvinyl chloride (PVC)
The bottom line is that smoke is visible particulate matter. The particulate matter in smoke is most commonly composed of carbon. Carbon in and around electrical equipment, left unaddressed, is a disaster waiting to happen.

Codes and Standards

The NEC is not silent with respect to this topic and Section 300.6, “Protection Against Corrosion and Deterioration,” is at the heart of this discussion. This section of the NEC reminds us that such equipment as raceway, cable tray, cablebus, cable armor, boxes, and more need to be constructed of materials suitable for the environment in which they are to be installed. Section 300.6 speaks specifically to ferrous metal equipment, aluminum metal equipment, and nonmetallic equipment. There are other references to this topic throughout the NEC in sections speaking to requirements of specific electrical equipment. As an example, in Article 358 for “Electrical Metallic Tubing,” Section 358.10, which talks about permitted uses of this equipment, 358.10(B) “Corrosion Protection” specifically notes that, “Ferrous or nonferrous EMT, elbows, couplings, and fittings shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection and approved as suitable for the condition.”

In addition to the NEC, UL Standards help us understand the tests and certifications to which products have been subjected. Listed products must be applied properly and must be subjected to environments not exceeding those to which they are listed to operate. A great resource to help us understand the limitations of products is the UL White Book (www. This is another great free resource for installers and inspectors for topics well beyond that of this article. Very well worth a spot on your bookshelf and a bookmark in your browser.

As discussed earlier, a fire is an unplanned event that changes the environment in which electrical equipment is installed. Because the environment changes during and after a fire, the design more than likely violates section 300.6 requirements. Because smoke and gasses can travel well beyond the immediate fire location, the damage to electrical equipment can be extensive and go unresolved.

NEMA Document

A recently published NEMA document, “Evaluating Fire- and Heat-Damaged Electrical Equipment,” can prove to help in the evaluation process of electrical equipment after a fire. This document is a free download available at www.nema. org. Electrical distribution equipment, motor control, adjustable speed drives, power equipment, transformers, and many more pieces of electrical equipment are designed to deliver power safely, tested to standards, and manufacture performance criteria. This equipment is not intended to be subjected to the caustic environments during and after a fire.

The presence of known or unknown corrosive agents in a fire event in particular can affect the physical properties of metallic and nonmetallic materials and the required corrosion protection for electrical equipment according to NEC Section 300.6. This new NEMA document can help you determine which equipment needs to be replaced and which equipment can be refurbished.

As always, keep safety at the top of your list and ensure you and those around you live to see another day.

Thomas Domitrovich, P.E., is a National Application Engineer with IEC Platinum Industry Partner Eaton Corporation in Pittsburgh, Pennsylvania. He has more than 20 years of experience as an electrical engineer and is a LEED Accredited Professional. He is active in various trade organizations on various levels with IEC, the International Association of Electrical Inspectors, the Institute of Electrical and Electronic Engineers (IEEE), the National Electrical Manufacturer’s Association (NEMA), and the National Fire Protection Association (NFPA). Domitrovich is involved with and chairs various committees for NEMA and IEEE and is an alternate member on NFPA 73. He is very active in the state-by-state adoption process of NFPA70, working closely with review committees and other key organizations in this effort.