What a GFCI protects against
A ground-fault circuit interrupter (GFCI) protects people from electric shock. It
continuously compares the current leaving on the hot conductor with the current returning
on the neutral. In a healthy circuit those are equal; if a few milliamps go missing —
leaking to ground through a person, a wet appliance, or damaged insulation — the GFCI sees
the imbalance and opens the circuit in a fraction of a second. A Class A GFCI is built to
trip at roughly 5 milliamps, well below the level that endangers a person.
This is the opposite end of the safety problem from an AFCI. The GFCI is watching for
current that escapes the circuit — a shock hazard to people — not for the arcing signature
that starts fires.
Where GFCIs are required
GFCI requirements live mainly in 210.8. For dwellings, 210.8(A) calls for GFCI protection of
receptacles in wet, damp, or grounded locations: bathrooms, garages and accessory
buildings, outdoors, crawl spaces, basements (all basement areas, not just unfinished ones,
in the 2020 and later editions), kitchens, laundry areas, and receptacles within 6 feet of a
sink. A separate list, 210.8(B), covers receptacles in other
than dwelling units, and it is broader still. The unifying idea is water and grounded
surfaces near people — the conditions where a ground fault is most likely to become a
fatal shock.
The exact list moves with the occupancy and the edition: dwelling kitchens, for instance,
require protection for receptacles serving the countertop and, in newer editions, others
nearby, and recent cycles extended coverage to certain 250-volt receptacles rather than
only 125-volt ones. When a question gives you a room and an edition, work from those facts
rather than a general impression.
Key rule: a Class A GFCI trips at about 5 milliamps of leakage to ground.
Anywhere water and people meet — baths, kitchens, garages, outdoors, basements — expect a
GFCI requirement.
How the requirement expanded by edition
Like AFCI rules, GFCI coverage has grown with each cycle, so tie your answer to the edition
in the question. Protection began decades ago at outdoor and bathroom receptacles, then
spread to garages, kitchens, basements, and laundry areas. The 2020 edition added
protection for certain 240-volt outlets and for outdoor outlets serving dwelling-unit
equipment such as HVAC, and pushed requirements further into non-dwelling spaces. The 2023
edition expanded coverage again to additional dwelling-unit appliances and locations.
Devices, GFPE, and GFCI vs AFCI
GFCI protection can come from a GFCI receptacle, a GFCI circuit breaker, or a deadfront
device, and a single upstream device can protect the receptacles downstream of it. Recent
editions also require these devices to be readily accessible so a tripped GFCI can actually
be reset. One distinction the exam likes: a Class A GFCI protects people and trips at about
5 milliamps, while ground-fault protection of equipment (GFPE) protects equipment and
conductors and trips at a much higher level — they are not the same device and serve
different purposes.
Both the GFCI and the AFCI are life-safety devices, but they solve different problems: a GFCI prevents shock by
catching current that leaks to ground, while an AFCI prevents fire by catching arcing
faults. Many kitchen and laundry circuits now require both, which is why dual-function
devices exist. On the exam, decide first which hazard the question describes — shock or
fire — and the right device follows.