Fixed wiring is the permanent wiring in the walls of a structure that connects things like wall sockets and light fixtures to a power source.
Renovations—especially the do-it-yourself kind—are a leading cause of electrical fires. Sometimes it's the tools themselves that cause them, thanks to frayed cords or not using extension cords appropriately.
However, most electrical fires are caused by problems with fixed wiring. Often, it's because the renovation adds an additional burden to existing electrical systems, and they can't handle it.
Goings-On Behind the Walls
Because electrical wiring is usually hidden inside walls, it's easy to not give it much thought. This oversight can and does lead to problems. According to the National Fire Protection Association, nearly 40,000 housefires and 350 deaths in the United States every year are caused by faulty home wiring and other electrical equipment such as plugs, lighting, and extension cords.
In the Nick of Time
If you're doing a remodeling that requires new wiring, get a permit before you start and have it approved by a qualified electrical contractor. If your municipality doesn't require these inspections (most do, however) or you can't find a qualified inspector, call your local fire department or building department for help.
It's especially a problem if you live in an older home, as the wiring in older homes wasn't designed to handle the higher demand that newer appliances place on it. Although it's true that today's appliances are more energy efficient than they were in the past, they're also bigger and we use more of them.
Problems like the following could very well be lurking behind your walls and in your ceilings:
Burned wire insulation in ceiling lights, typically caused by using bulbs with higher wattage than old fixtures can handle.
Frayed insulation around lights. Using improperly sized bulbs causes this, too.
Damaged insulation around fixed wiring. This happens over time from wires rubbing together. Nicks in the insulation or overloaded circuits are other culprits. Wires get hot, and the heat buildup causes insulation to crack or fray.
Arcing takes place when an electrical current jumps through a tiny gap of air.
All of the above can cause a nasty little phenomenon called arcing, which is pretty much what the name implies: electrical current jumping between two things. Here, the current leaps through the air between the ends of broken wires or at loose receptacle connections. The energy from the current heats up the surrounding area, causing you guessed it, a fire. If there's not much oxygen to feed it, it can smolder for hours before bursting into flames.
Devices called arc fault circuit interrupters (AFCIs), which are installed in circuit-breaker panels, detect arcs that are so subtle that they typically don't trip circuit breakers. They're not a substitute for good wiring, but they do offer a measure of protection for older or damaged wiring. If you're in an older home, consider having them installed. If your home was built after January 1, 2002, circuit interrupters were installed on all bedroom circuits, as per national electrical code requirements.