Should You Freak Out If Your Outlet Sparks?

You've just put your infant to bed, or perhaps slid your copy of "X-Men No. 7" into its acid-free archival sleeve for the night. You tiptoe to the door and realize you forgot to plug in the baby monitor or the "Mission Impossible"-style array of laser beams surrounding your comic book vault. As you push the plug into the outlet, you notice a tiny spark in one of the receptacle slots. Well, you think, that's it. You have to find a new place to live now, and you'll stand there with a fire extinguisher until the moving van arrives.

Don't panic. You need to get to the bottom of it as quickly as possible, but odds are that what you just experienced isn't merely normal, but universal. The spark you're seeing is what happens when an electric current jumps a small distance from one conductor to another. It's what happens when static electricity jumps from your finger to a doorknob, and it's what happens when a bolt of lightning strikes the ground. 

Harmless sparks are extremely common; more dangerous ones look and act differently, and are referred to by electricians and home inspectors as electrical arcs. And remember: it's always a good idea to call a professional to get a second look at any potential electric concerns.

Harmless sparks happen every time you plug in (or unplug) a device that's turned on or complete a circuit by turning on a switch. Yes, it happens every single time, though you probably don't see it very often. What's happening is that electricity, in its relentless eagerness to complete a circuit, is getting a little ahead of you and jumping over the tiny gap between parts that are about to touch ... in this case, the plug's prongs and the metal contacts in its receptacle. These are small, blue sparks that are gone in an instant and are accompanied by no other drama.

Even if you resist the reassurance of experts that these sparks are harmless, it's practically impossible to avoid them. If you only plug in things that aren't turned on, that wouldn't help, because most switches experience the same spark between contacts when you flip it on or off. Fortunately, you have nothing to worry about. 

And even if you can't tell the difference between harmless sparks and dangerous arcs, there's a good chance your outlet or circuit breaker can if they're equipped with arc-fault circuit interrupter (AFCI) protection. These little, ubiquitous sparks won't trip your breakers even if the breakers are AFCI-protected. And because AFCIs are good at distinguishing dangerous arcs from harmless ones, so-called "nuisance tripping" of AFCI-protected circuit breakers (that is, breaker tripping that happens frequently) is usually caused by something other than the minor sparks created when plugging in a device.

Nuisance tripping is rarely a thing. Some electric motors can trip AFCI breakers repeatedly, but if something in your outlet wiring is causing your breaker to open the circuit, you need to deal with it. Hazardous arcing is relatively uncommon within outlets themselves, but worn contacts inside aged outlet devices can cause arcing. Other sources are cable connections that loosen over time (a common cause), moisture from leaks within a wall, worn or damaged wires attached to the receptacle, or even wires stripped more than necessary for connection to your wall box device. 

If sparks are anything other than blue (yellow or white, for example), are larger or take longer than an instant to disappear, or are accompanied by burning smells, you almost certainly have an uncommon but dangerous problem on your hands. This is also true if sparks are coming from any place, like an electric cord, where there's not a connect/disconnect mechanism.

The reason is pretty straightforward. Any sustained arcing between hot- and ground-connected parts of a circuit constitutes a short circuit, which invariably come with unsafe levels of heat (the same heat that's used in arc welding), so arcs are among the most common cause of home fires. AFCI circuit breakers detect changes to a current's waveform that are signatures of arc faults and shut down the circuit quickly when an arc occurs. Unfortunately, not all circuits are required to have AFCI protection, and older homes might not have AFCI breakers or receptacles at all. Luckily, they're easy to install — and quite a bit cheaper than buying a new house.