Fire and Electricity
Fire and Electricity |
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Fire emergencies represent dangerous emergency situations. There are three components that must be present at the same time for a fire to occur:
A chemical reaction combines with the fuel, heat and oxygen to start and maintain a fire. Fires involving electricity generally have two causes. One is overheating and the other is arcing. Overheating happens when the amount of current flowing is more than the electrical equipment is designed to carry. This is known as overloading. An arc is a sudden electrical flash between two points. Arcs are very hot and emit ultraviolet radiation. They easily ignite nearby combustible, flammable or explosive material. Electrical arcs are often linked with some sort of short circuit or interruption in the current flow.
Other contributing factors to an electrical fire can include:
Fires have been divided into four main classes. These classes are A, B, C, and D. This classification system relates to the type of fuel being burned in the fire. This classification is important to understanding how to extinguish a fire. Depending on the fuel, different actions will need to be taken in order to properly deal with the fire.
For Class A, B and C fires, the removal of any one of the three necessary components will extinguish the fire. You can either get rid of the fuel, the heat or the oxygen.
| Remove the fuel |
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Result: Starvation |
| Remove the heat |
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Result: Cooling |
| Remove the oxygen |
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Result: Smothering |
With regards to an electrical fire, you might be able to remove the energy and the heat by disconnecting the electrical power. As well, the use of extinguishers specially designed for electrical fires might help to cool and smother the electrical fire.
Portable fire extinguishers, also called "first-aid extinguishers", are the first defense against fire. During combustion, the burning process will continue as long as there is sufficient fuel, heat and oxygen to sustain it. The process must be "interrupted" by means of an extinguishing agent - a fire extinguisher. Portable extinguishers are classified according to their ability to handle specific types of fires. Extinguishers must be readily accessible, properly maintained, regularly inspected, and promptly refilled after use.
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Class "A" Extinguishers: For fires in ordinary combustible materials such as wood, paper, and textiles where a quenching, cooling effect is required. A triangle with a green background containing the letter "A" should identify extinguishers suitable for Class A fires. Background colour: green. |
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Class "B" Extinguishers: For flammable liquid and gas fires, such as oil, gasoline, paint, and grease where oxygen exclusion or flame-interruption is essential. A square with a red background containing the letter "B" should identify extinguishers suitable for Class B fires. Background colour: red. |
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Class "C" Extinguishers: For fires involving electrical wiring and equipment where the non-conductivity of the extinguishing agent is crucial. This type of extinguisher should be present wherever functional testing and system energizing take place. A circle with a blue background containing the letter "C" should identify extinguishers suitable for Class C fires. Background colour: blue. |
There are many types of fire extinguishers. With these different types of extinguishers, the methods of operation, and the classes of fires that they are intended to extinguish are different. The list that follows provides some insights into SOME of the different types of extinguishers that you may encounter. Please read through the list to get a sense for when different types of extinguishers might and might not be appropriate.
When battling an electrical fire, it is best to use a non-conductive extinguishing agent. However, there may be cases when this is not possible, or when it is necessary to use what you have available in order to protect life and/or property. In these cases, when it is absolutely necessary, it is permissible to use a FOG NOZZLE to spray fresh water on electrical fires. Extreme care must be taken in this situation. It is necessary to adhere to a minimum safe distance in order to use water to help combat the emergency situation involving electricity. When arriving at the scene of an emergency involving electricity, it will often be difficult to know or be able to find out the exact voltage of the involved lines or equipment. Therefore, A minimum distance of 10 metres (roughly 33 feet) must be maintained between the fog nozzle of the water hose and the live wires and/or equipment.
In the case where personnel of the local power supplier are present to determine the exact voltage of the lines and equipment involved, then different approach distances may be safely used. The associated nozzle pressure of the water hose must be at least 700KPa (about 100 PSI). Under no circumstances should the emergency responder approach closer than the minimum distances referred to in the regulations in your geographic area. The provincial regulation for the province of Nova Scotia have been detailed in the next section.
Some emergency responders have access to vehicles with extension options. Always be careful concerning the placement of these extension devices in relation to power lines. If you are fighting a fire involving electricity and have the choice between being on the ground or on a truck with a mounted water cannon, you would be safer on the truck. Remembering that electricity seeks all paths to ground, if you are on the truck you are almost like a bird on a wire: If electricity followed the water stream it would not pass through you to ground as everything is at the same level of energization. On the ground, you do not have this added protection.
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To summarize, with regards to our specific interest in electricity: Fires involving electricity are known as "Class C" fires. The best type of extinguisher for fighting an electrical fire is a "Class C" Extinguisher that has a symbol with the letter C and a blue background. |
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