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Here's some information from the Walters Forensic Engineering company on how electricity can cause fires, "The three main groups of fire causes are accidental, natural and incendiary. Of the accidental fire causes, electricity often plays a major part. Electricity can also be involved in incendiary and natural causes. Fire investigators are faced with difficulty in determining the cause of a fire, they have often relied on the phrase 'the fire was electrically caused' as a 'catch all' to avoid the more appropriate phrase 'the fire cause was undetermined'. In fact, it is actually quite difficult to start a fire with electricity.

Three elements must be present in order for a fire to initiate. These are oxygen, fuel and heat. Not only do these elements have to be present together at the same time, but the fuel must be conditioned in a way that the heat source can initiate an exothermic oxidation reaction. Electricity can play an important role in this process by providing the heat source.

Short Circuits

"One example of an electrical heat source is a short circuit. There exists two main types of short circuits; a dead short circuit and a limited short circuit."

If the circuit is not fused properly, the current can continue to pass through the wires causing them to overheat - which can ignite surrounding combustibles causing a fire.

In the case of the limited short circuit, "Wires come in contact such that the volume of material through which the current flows is smaller than the fusible link. This will create a spark or flash and result in melting of the copper of the wiring. This situation can also cause ignition of combustibles provided the mass of the combustibles contacting the heat source is small enough that the heat source can cause it to reach ignition temperatures and initiate a self-sustaining exothermic oxidation reaction or fire. Cotton products, sawdust, wood chips and combustible gases can be ignited."

Overloaded Circuits

"Over fusing of a circuit can result in high current flow through the wires overloading the circuit. Although electrical wiring is designed to carry current at much higher than its rated capacity, increasing current above this rated capacity causes the wire to generate excess heat. if the wire is enclosed within a small insulated space, such as the holes through which wires run through floor joists in a home, the heat in these areas may not be able to dissipate as quickly as it is being generated. As a result, the surrounding combustibles can pyrolize and eventually ignite, causing a fire."

Leakage Current

"Fires can also be caused electrically through what is called leakage current. Leakage current occurs when water is in the presence of electricity. Exposed wiring, which exists primarily at connectors and switches, can come in contact with water. Since water conducts electricity, a current will flow through the water between contacts or from the live to ground or common."

Electrical Contacts

"Electrical contacts can also fail resulting in uncontrolled heating. Each time a contact is opened or closed, a small spark is generated. This causes degradation of the surface of the contact."

Check out the rest of the article that discusses how the investigators must assess liability.

A great way to insure the protection of your home or business is to have regular inspections by an electrician. And, as a backup to regular inspections and maintenance, you might want to consider adding fire sprinklers - it can reduce damage and lower insurance costs, as well as protect your family or employees. If you need to find a local sprinkler company, check out our blog on Fire Sprinkler Installation for more details.

Labels: Electrical Inspection, Electricians, Fire Safety