Home electrical fires are preventable, but they happen all the time. Don't let it happen to you and be particularly careful in the holiday season. | Source
Electrical Fire Causes
Unfortunately, home fires are an all-too-common occurrence. In many cases, the root cause is an electrical failure of some kind. Sometimes it is set off by a mechanical failure of an electrical device, and other times, it is due to improper usage or design of the electrical system in your home.
Nearly all electrical fires can be prevented, though, if we understand the causes and take appropriate steps to prevent them.
Poor Electrical Connections Can Cause a Home Fire
Any time electricity flows it creates heat. Under normal conditions, this heat is minimal - your home wiring is designed and installed to prevent any large amount of heat build up in the electrical system. Sometimes, though, failing equipment or devices create far more heat than they are designed to. Some examples might be:
Loose or Worn Outlets
Loose and worn outlets. If cords can be plugged into an outlet very easily or if they simply fall out as time passes, the outlet needs replacement. If appliances plugged into an outlet operate only intermittently it can be caused by poor connections either in the outlet itself (outlets with wires plugged into the back of them instead of being secured by a screw will fail with time) or in wire nuts in the box behind the outlet. Either tighten the wire nut connections and/or again replace the outlet.
Worn Switches
Like outlets, switches will wear out over time. They will usually last for many years, which makes it easy to think they will last forever, but they won't. Just like outlets, the wire connections in the back or side of the switch may be loose and, again like an outlet, the switch needs replacement. It is also possible that wire nuts are loose behind the switch.
Old and Corroded Fixtures
As electrical parts age the wiring degrades very slightly each year. A light fixture may be good for 25 or even 50 years, but eventually the wire insulation inside chars, the connections corrode and the light bulb sockets won't hold a bulb well. If lights flicker or won't stay lit and potential switch problems have been eliminated it may be time to replace old light fixtures.
The spring that holds the wire in the small hole weakens over time and makes for a poor electrical connection. | Source
Changing this flickering light fixture found the old wire to be charred at the ends of the wires with both wire nuts loose. A fire waiting to happen. | Source
Other Electrical Problems That Can Result In a Fire
Extension Cord Issues
The use of extension cords should be evaluated for necessity; they are a very common cause of home fires. When a cord is kinked or smashed (if it has been walked on it too many times, for instance), the electrical resistance of the wire inside rises, which creates heat. Eventually, the insulation may well begin to melt but this is not obvious; it may just be a small portion between the copper wires inside. As this happens more and more current begins to flow between the wires and eventually causes a fire. If you absolutely must use an extension cord for long periods of time make sure it is completely out of the way and not subject to physical damage. Under a couch, perhaps, or tucked into the edge of carpeting - whatever it takes to make sure that feet, vacuum cleaners, pets and small children can't reach it. Better to simply add a new outlet to an existing one than use an extension cord for months or years.
Continual Overloads
Many older homes are really marginal in their ability to safely provide enough power to operate all the electrical things we use in modern life. There just isn't enough power available to the home or there aren't enough individual circuits. In years past only one circuit was designed into kitchens, and that isn't enough to properly operate a microwave, refrigerator, toaster, electric grill, mixer, toaster oven, etc. The result is that the circuit breaker or fuse is always tripping. The same is true in bathrooms; the bathroom circuit commonly supplies bedrooms as well, but add in a curling iron and a hair dryer along with the bedroom TV and electric blanket and that circuit is often overloaded as well.
Every time a circuit trips or a fuse blows it is an indication that the circuit is overloaded, but most people will simply reset the breaker and do it again. The inevitable result is that the circuit breaker is slowly damaged to the point it doesn't work properly anymore and the panel itself can be damaged as well. As an electrician, I've seen house panels that have the massive bus bars inside, carrying the entire power for the whole home, half melted from repeated overloads and this is a recipe for disaster - it most certainly is one way that home fires start.
If you are commonly tripping a breaker or having to replace blown fuses, have additional circuits installed as necessary. It can be expensive but it's better than burning the house down.
In addition to electrical overloads is overloading a light fixture with lamps that are too large. According to the NFPA, the largest source of electrical fires are lamps and light fixtures. Such fixtures are designed to withstand only the heat from the rated size light bulbs - do not overload the fixture with bulbs that are too large. While it is quite acceptable to use a 100 watt equivalent CFL bulb to replace a 40 watt incandescent bulb as an energy saving measure in your home, the key is that the CFL is only using a few watts of energy and isn't nearly as hot. It won't overload either the thermal insulation or the electrical wiring of the fixture. It isn't the same as screwing in a 100 watt bulb into a 40 watt light.
Defective Equipment
Occasionally equipment of various kinds can fail in such a way that it may not trip a breaker or blow a fuse, but is still drawing more current than it should. Circuits in general are allowed to carry only 80% of the current the breaker will allow as a safety factor but when that is removed the safety becomes marginal. While the current may not trip a breaker, it does cause heat and, over time, can harm the electrical components such as breakers or the wire itself. Eventually resistance rises to the point that enough heat is produced to cause a fire.
If a fan, for instance, turns too slowly, if the cord warms to the touch, if it makes strange noises - replace or repair it! Don't simply keep using it until the cord catches fire. Electrical heaters are equipped with a "tip over" switch that turns them off if they are tipped over - never, ever defeat such electrical protections. They can be irritating, but they also save lives.
Improper Wiring Methods
A qualified and conscientous electrician will always follow the requirements of the NEC to produce a safe and effective electrical system, but the same isn't true of homeowners who often don't know what is safe. Another example from my experience: I once purchased a used hot tub from a homeowner. Upon finding that I was an electrician, he asked me to unwire it from the house and I agreed to help him out there. He had run wire from the hot tub to a dryer outlet just inside, but what appeared to be adequately sized wire turned out to be 14 gauge wire wrapped with many layers of electrical tape. Now, that is at least 3 sizes too small for the hot tub and when I removed the large cover from the dryer outlet it simply crumbled in my hands - completely charred to nothing but tiny bits of plastic just waiting to be disturbed to fall apart. The homeowner looked at it, looked at me, and commented that "I guess that's what causes fires, huh?".
He was right - that's what burns homes down and it was completely unnecessary. If you don't know what is needed to complete a wiring job safely, either find out or hire someone that does know. Electricians have, in most states, completed years of study and work learning how to ply their craft and are usually quite knowledgeable. Hire one if necessary.
Holiday Decorations
Holidays often bring home fires with them. Extension cords are strung everywhere, lights are added all over rooms and vegetation outdoors, and even candles are left burning without supervision. All of these are dangerous and can cause a home fire at the worst possible time. Make sure that your Christmas tree isn't drying out with lights or candles still on it. Put candles out when you're not right there. Protect extension cords, and particularly don't leave the ends of them in puddles or snow. Arrange cords so that children or pets can't play with them; a dog chewing a cord can not only electrocute themselves but can burn the house down as well. A little common sense can go a long way.
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A damaged extension cord. Either replace or repair properly - never simply throw some tape on it. | Source
The National Electrical Code (NEC) is widely accepted throughout the US as the definitive standard for electrical work. A good portion of that code consists of procedures to prevent fire. I have been a professional electrician for many years and I am expected and required to understand and comply with the guidelines of the NEC at all times. That typically includes an understanding of why those rules are in place.
The NEC's Role in Home Fire Prevention
The NEC, some 800 pages describing proper methods of doing nearly all electrical work, is just a small part of the NFPA - National Fire Protection Association. It is not designed to produce efficient electrical systems nor to make profits for the inspectors enforcing the rules. It is not intended to sell particular electrical devices and it will not describe how to wire a house cheaply or quickly. The only reason for the code is safety - all 800 pages describe how to install electrical systems that will operate safely and this includes fire prevention.
For example, table 310.16 in the 2008 code lists the minimum wire size for a given circuit breaker or fuse - in the table we can see that a 20 amp breaker requires a 12 gauge wire. This isn't because a smaller 14 gauge wire won't work, it is because a 12 gauge wire will carry at least 20 amps of current (with a considerable safety factor) without overheating and causing a fire. If your home is wired with 14 gauge wire (most homes are) but the breaker keeps tripping it is not only illegal but very risky to replace it with a 20 amp breaker. That 14 gauge wire can now overheat before the breaker trips and cause a home fire, and that's the first lesson for the homeowner - never make changes to the electrical system in an effort to bypass the safety devices installed.
GFCI outlets, circuit breakers, fuses, arc-fault breakers - all of these can be irritating at times but they are there for a very good reason - your safety and the safety of anyone in the home. They are designed to shut the circuit off before either a fire or shock can cause any harm and should never be removed, modified or defeated in some manner.
In years past homeowners with screw in fuses rather than modern circuit breakers used to remove the fuse, stick a penny in and screw the fuse back in. Any and all protection afforded by the fuse is completely lost as a result and overloaded circuits will simply heat up until they either melt the wire in two or (more likely) cause a fire. Such modifications all too often have literally deadly results.
The "bible" of electrical work. Follow it and you will have a good, safe electrical system. | Source
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
QUESTIONS & ANSWERS
If you leave an older television on constantly, can that start a fire?
Not unless the TV is somehow defective. Older televisions were (and are) designed to run for hours and hours at a time. Leaving one on day and night won't do anything but run your up electric bill. Those old CRT TVs took a good bit of current.
While working on a remodel, two adjacent outlets touched at the screws on the side of the outlets. Sparks and smoke occurred and the breaker tripped. The outlet screws on the sides that touched are now black. Do I need to replace the outlets completely to be sure they are safe?
There is a good possibility that they are both damaged to the point of replacement. Even if not, however, the small cost and effort dictates that they should be. Replace them as a safety measure if nothing else.
Can a switch that’s turned on cause a fire even if it is not being used?
It would be unusual, but possible as long as the circuit is hot. The small springs inside the switch gradually go bad, causing resistance and that resistance causes heat, which causes a fire. The same for the terminals, particularly the ones on the back that hold the wire with springs rather than by tightening a screw.
I had a small power transformer that was defective catch fire. Fortunately, no disaster occurred. However, the circuit breaker on that circuit did not trip. Should it have? Do I need to have an electrician look at it to see why it didn’t trip?
It is possible that there was never enough current draw to trip the breaker, but it would be unlikely. You should either simply replace the breaker (it is an easy and inexpensive task) or have it tested. If you do call an electrician I would suspect that they will simply replace it as breakers are so cheap as to not be cost effective to test. Most breakers cost on the order of $10 and take 10 minutes to replace.
An insurance company is saying that an extension cord that I replaced an end on caused a fire but the cord cap isn't burned, and it still has the paper price sticker on it that looks new, and there was nothing that was plugged in was turned on. The cord is melted about 6 feet away from the cord cap, but that's where the fire was. What should I do?
You might hire an investigator yourself, and certainly should take lots of pictures. You will need that cord to determine the cause, though, to make sure that it was not damaged at the burned spot before the fire. If it can be done; I am not an investigator.
It doesn't sound like the insurance company is blaming your work; just the cord. Be aware that that is why extension cords should never be a permanent solution to lack of outlets; they are often damaged and/or overloaded and cause fires. Extension cords are one of the most common causes of fires for just that reason.
Sometimes. One might have the odor of ozone if a sparking action is occurring, or insulation or other material might be smoldering. Usually, though, there isn't much to detect.
I leave ceiling fans on low running while we are away on vacation to keep the air in our home circulating. Our neighbor says that ceiling fans are a major cause of fires and should be turned off. Can ceiling fans truly cause fires? They are all new ceiling fans, installed 5 months ago.
No. It is true that a defective fan could conceivably cause a fire, but so can any device. It is also true that a breeze will fan the flames to some degree (small, with the fan on low speed), but the fan is not then the cause of the fire.
If the circuit is turned off at the breaker panel, there is no source of energy to cause a fire.
However, if the breaker is turned on, but there is a fault somewhere in the circuit that prevents it from being used, then absolutely it can cause a fire. An example might be an outlet circuit with a poor connection that will not let power to the outlet. That connection can easily heat up enough to cause a fire.
Why do electrical outlets stop working? Is this caused by tripped circuit breakers?
If the circuit is still live at the outlet, it is likely due to weakening of the springs that hold the plug in or a bad connection of the wiring to the outlet.
If the outlet is truly dead - no voltage on it whether a lamp or something works or not and no voltage in the wires feeding it - it is common to find it is GFCI protected, with the actual GFCI located elsewhere in the home. It is also possible that a poor connection on some other outlet is causing the problem; it doesn't need to be the one in question that is causing the actual problem. A splice in a wire nut, in the questionable outlet box or a different one, can cause an outlet to go dead.
Worst of all is a poor connection somewhere on that circuit. That will leave voltage on the outlet, but it won't work. Tracing such a problem can be a tedious task.
I replaced several outlets in my home several months ago. Everything works as it should. However, I get paranoid about this sort of stuff. How tight of bends am I allowed to have in the 12 gauge wire? I wired them all back they way they were before; I didn't make the wires longer or shorter. I'm just worried that they are bent too tightly and that I should have lengthened the wire. Would an electrical problem have presented itself by now in my home if it was going to? Its been about a year with no issues
Unless you used pliers or another instrument to smash the wires into the smallest possible bend you need have no worries. Simply pushing them back into the box when installing a new outlet will not make bends too tight.
The terminals can very slowly loosen, causing resistance at the point of connection. This causes heat, which can start a fire. Connections internal to the switch can also degrade over time, doing the same thing. And it is possible for a switch to turn a device on when it should not be, potentially starting a fire.
Can a bare copper ground wire running across the floor of my garage attic be stapled down to a wooden floor?
Yes, but if that is living area, it's a definite no-no. If it is used for storage or anything else, it is a "no". At the same time, wires are always stapled to the top of trusses or joists, and those trusses or joists are often used for limited storage, so unless that space is commonly used in some way, I wouldn't worry too much about it. You will just have to be careful in the future not to set anything on that wire and certainly not to step on it. In this case, the problem is not so much creating a fire hazard because of the wire in contact with wood, it is in possibly damaging that wire in the future, which could either cause a fire hazard or even eliminate the ability to carry current completely and thereby create a shock hazard somewhere else.
Can a device or circuit catch fire if the power supply is off?
If a power supply, internal to a device such as a power supply in a computer, is off the circuit can still catch fire. An extension cord may be in use, for instance, or a wiring fault inside the wall. It is even possible, however unlikely, that there is a fault in the on/off switch which could cause a fire.
But if the power is turned off at the fuse box (and there are no batteries in use), there can be no electrical fires on that circuit.
I recently had a 3-way light bulb blow out, and when I tried to unscrew the bulb--it broke. To my surprise, the filament was still working, providing light. However, my husband was upset saying I should have alerted him because a fire could have started from the exposed filament. Is this really possible?
Light bulbs work by heating the filament white-hot; so hot (as in the thousands of degrees) that it glows brightly with very white light.
If that bare, 2,000 or 3,000-degree filament comes into contact with something flammable (a curtain, perhaps, or your shirt) an instant fire is almost inevitable.
Can having too much air conditioning in my house cause a fire?
Highly unlikely. Consider that there are very large, house-sized, freezers. The electrical system will, of course, have to be properly sized to handle the power draw.
My bathroom fan caught fire. We put it out with an extinguisher. It tripped the breaker. Can I reset the breaker and not turn on the fan switch?
Not a good suggestion. First, someone else may turn on the switch. But beyond that there may well be burned wires in the fan, which are shorted out and could start another fire. Best to leave the breaker off until the fan can be removed and wires safely inspected and capped off.
I replaced a light switch about seven years ago (switching from almond to white), today the switch made a crackling noise the light flickered and didn't stay on. When I turned it off and on again it turned on. Is the switch failing or the outside light?
Either the switch is failing or there is a loose connection. A failing light will not make the switch crackle. Switches are cheap enough, and the work simple and quick enough, that the switch should replaced as a preventive measure.
We just had a storm roll through and half of my house is without power should I be worried about something catching fire?
Probably not. It sounds more like a problem with the power company than anything. You might check anything that operates on 240 volts though, and if it isn't operating properly turn it off until you get power back.
I recently purchased an electric vehicle and the only outlet I have available also has a small 5 CF freezer attached to it. Would using my 110v EV charger on the same outlet as the small freezer cause a fire?
No. However, it may blow the breaker, depending on the draw of your charger. I strongly suggest checking for that problem often - you don't want the freezer to stop cooling and never know about it. My EV can be set to use either 15 or 20 amps - if yours is similar you will have to use the smaller setting. I will also say that it is unlikely you will be pleased with the setup; 100V charging of an EV takes a very long time. My Chevy Volt, which is a plug-in hybrid with a smaller battery, not a full EV, takes as much as 12 hours. You will probably end up buying and installing a larger charger, on a dedicated circuit.
The cord on my vacuum hasn't been working properly, I plugged into the socket and it caught fire, I unplugged it and it stopped. Is it the electrical or the vacuum cord?
Assuming you mean that either the cord or the vacuum caught fire, the problem is one of those. If you mean there was a fire in the electrical outlet, the problem is in the electrical system. Either the outlet or the breaker that didn't trip when it should have.
I have an air conditioner plugged into an outlet. It does not feel loose, but it won’t work unless I jiggle it so that it is at a slight angle, by pulling it so that it is just a touch further in on the left than on the right. What could be causing this?
Sounds like the outlet is ready for replacing. An easy task that won't cost more than a few dollars.
Can electrical wires start fires even when not being used or turned on? Things such as lights in ceilings or outlets?
An outlet always has power to it as long as the breaker is turned on, so yes it can start a fire when there is nothing plugged into it. A light fixture that is turned off, on the other hand, would be very unlikely to cause a fire. There would have to be something else wrong somewhere else in the house, plus something wrong in the fixture.
I have Christmas lights on a wreath outside a bedroom window, with the cord coming through the window, plugged into an outlet beneath the window on the inside wall. Is it safe to just turn the cord switch off at night or should I unplug the entire cord?
If you are smashing the cord by closing a window on it you should simply remove the cord permanently and give up on the idea completely. If both the lights and the cord are rated for outdoor use, and you aren't closing the window on it, then it should be fine.
It just might be possible if the surrounding environment and materials were very flammable. But few, if any, devices are built that way, and even if they were there is still the housing containing the material to burn through. It would be very, very unlikely to have a circuit board cause a house fire.
We rent a studio and in a Victorian house that was made into 4 studios. Apt 2 and apt 3 are on the same breaker panel. For the last few weeks, their power keeps going out. I noticed that now their panel has black duct tape to hold them down in place. Can this be an issue?
If duct tape is being used to keep a breaker from tripping when the circuit is overloaded then yes, it is a problem. A big one.
Breakers blow because the circuit is overloaded and carrying more current than it is designed to do. That means that the wiring on that circuit is overheating, and THAT means there is a fire hazard, so the breaker blows and stops the hazard from happening. Prevent that action somehow, letting the hazard grow, and the next step is to rebuild after the fire.
Can a socket that has blown a fuse cause a fire? If so how long after would the fire start?
Absolutely, an outlet that has blown a fuse can start a fire. If the problem was whatever was plugged into it, and that item is no longer there, there should be no problem, but if the problem was within the outlet itself it should be repaired immediately. The time to a fire could be from 2 minutes to 2 years. Or never. No way to tell.
Can a slight spark in an old fuse box cause a fire, why is there a little spark from the old fuse box?
There should be no sparking inside a fuse box, and that there is one indicates there is a possible cause for the fire. The reasons for a spark are far too numerous to go into; I recommend getting it looked at immediately.
I have mice behind my stove. Can I use expandable foam to fill the holes around the pipes and outlet?
You can. Just make sure you don't fill it with so much that after expanding it puts too much pressure on the wallboard, piping, and other items there.
But that may not be the best answer to the mice problem, as they may chew right through it. Another option is to fill the holes and spaces with steel wool, as rodents will not chew through that.
I hung pendant lights that just plug in with no wiring necessary. One of them blew out after an hour, but it was not the bulb. One of them melted at the wire and came crashing to the ground and shattered in our face! We took the other two down after that. The outlets are up in a little groove in the ceiling which I thought was strange. Were these lights incorrectly installed?
Is it possible that you have low voltage pendants plugged into 20 volts? Other than that it does sound like either they are garbage, or the outlets were installed improperly. Certainly, if they are melting the wire, they should not be used until an answer is found.
Why isn't it a safety issue when connecting a short wire with a light in a circuit?
If you're referring to something like a lamp cord, from a lamp to an outlet, it has to do with the resistance of the wire, and a short wire has very little resistance. A wire the same size but 100' long will have far more resistance and create more heat as a result.
If you use a bulb with a higher wattage than the fixture is designed for, it can absolutely cause a fire. Note, though, that fluorescent bulbs (the "twisty" kind used to replace an incandescent bulb) and led bulbs are usually listed as being an "equivalent" wattage to an incandescent but actually draw far less current and those bulbs can be used in a larger equivalency than the original incandescent bulb.
In addition, long term use of a fixture (meaning decades) will eventually dry out the wiring insulation and that can be a fire hazard. Not the fault of the bulb, just the result of years and years of heat.
I recently had a garage fire. I hadn't been in the garage in over a week. Nothing was on and the door was locked. It has been ruled electrical. What could've caused the fire to start?
It is entirely possible for a piece of equipment, or even an outlet or light switch, to develop a very minor short in it. Just a trickle of power and nowhere enough to trip a breaker.
But it can be enough to heat the device or wires and, very gradually, deteriorate the insulation. Over time it gets worse and worse until there is enough heat being produced to start a fire.
Animals, perhaps mice or termites, even a bees nest, can cause damage to wires with the same result - a minor short that is enough to build heat over long periods to the point that a fire starts. I once worked an industrial site that had a large well with automatic switch gear in the well house to start and stop the big pump. A squirrel got inside and got across the main, 480V, terminals. It was electrocuted of course, but remained there, causing a short between the two terminals. The resulting fire was contained within the metal box, but the entire relay had to be replaced.
There’s a big hole in my basement ceiling that allows wiring to go up to my dishwasher above. There is a single wire running from the basement through this hole and up to the upstairs level. This hole is big enough for a rat to go through, let alone a mouse. I stuffed steel wool in that hole around the wire so that mice cannot go through it. Is this a fire hazard?
No, some steel wool in a hole should not be a big fire hazard. But be aware that if there are mice in your basement, closing off one hole to the upstairs is not going to keep them out of that area.
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