GFCI & AFCI
Protection

Two different dangers: shock vs. fire

Most homeowners lump GFCI and AFCI together as "those outlets that trip." They're not the same device, they don't watch for the same thing, and confusing them leaves real holes in a home's protection. Here's the plain version:

• A GFCI (ground-fault circuit interrupter) protects people from shock. It watches the current going out on the hot wire and coming back on the neutral. In a healthy circuit those two numbers match. If some of that current finds another path — through water, through a damaged cord, through you — the GFCI sees the mismatch and cuts power in a fraction of a second, before the current through a body reaches a dangerous level.
• An AFCI (arc-fault circuit interrupter) protects the house from fire. It watches the shape of the current for the jagged electrical signature of arcing — the sparking that happens at a loose terminal, a nicked wire, a cord crushed under a furniture leg. Arcing can smolder inside a wall for months before it flames. The AFCI is listening for exactly that.

One watches the balance of the current; the other watches its character. A GFCI does nothing about a wire arcing inside a wall. An AFCI does nothing about you dropping a hair dryer in the tub. A protected home needs both, in the right places.

Why your house may only have half the picture

GFCI requirements have been in the code since the 1970s, phased in room by room — bathrooms first, then kitchens, garages, exteriors, basements, and more over the decades. AFCI requirements arrived much later (bedrooms first, around the turn of the 2000s, then most living areas after that). Put those timelines against the age of Pittsburgh-area housing stock and you get the reality I see on calls:

• Pre-1970s homes: often no GFCI protection anywhere, two-prong receptacles, and sometimes no equipment ground at all.
• 1970s–1990s homes: GFCI in a bath or kitchen (maybe), nothing anywhere else, and that one device may have quietly died years ago — they have a finite life, and a dead GFCI often still passes power while protecting nothing.
• 2000s–2010s homes: GFCI in the wet locations, AFCI in the bedrooms only.
• Recent construction: both, across most of the house.

The chapters ahead walk through where each device belongs, how they work in enough detail to make good decisions, how to test them so you know they're alive, and how to read a trip — because a tripping device is a message, and "reset it until it stops complaining" is not a diagnosis.