What tamper-resistant receptacles protect against
A tamper-resistant (TR) receptacle contains spring-loaded plastic shutters behind each slot.
When the shutters are at rest, they cover the energized contacts so that inserting a single
object into one slot — a coin, a key, a hairpin — meets a physical barrier rather than a live
terminal. The shutters only open when both slots receive simultaneous, equal pressure, which
is what the two prongs of a standard plug provide.
The hazard being addressed is the classic childhood electrical injury: a child inserts an
object into a single receptacle slot and receives a shock or burn from the energized contact.
Ordinary plastic outlet caps were the traditional workaround, but they can be removed, lost,
or forgotten. Because the TR mechanism is built into the device itself, the protection is
always present regardless of how the receptacle is used over its life.
TR receptacles are not the same as GFCI devices. A GFCI interrupts
the circuit when it detects current flowing to ground rather than returning through the neutral.
A TR receptacle is a mechanical guard — it does not interrupt the circuit at all; it prevents
unwanted contact from occurring in the first place. Locations that require both a GFCI and a
tamper-resistant feature can be served by combination GFCI/TR devices, which are widely available
and satisfy both requirements with a single device.
Where tamper-resistant receptacles are required
Section 406.12 is the governing provision. Dwelling units are the foundational required location:
receptacles installed in dwelling units must be listed tamper-resistant types. The code does not
limit this to receptacles in rooms children are likely to be in — it applies to receptacles
throughout the dwelling, including garages, basements, and outdoor outlets.
Beyond dwelling units, the required locations have expanded in recent NEC editions. Without
attributing specific changes to specific editions, the categories that have been added over time
include:
- Guest rooms and guest suites in hotels, motels, and similar transient lodging.
- Child care facilities — spaces intended for the care or supervision of children.
- Pediatric care areas in health care facilities.
- Waiting rooms and certain assembly areas where children are likely to be
present, in some editions.
When the exam names a specific edition, answer for that edition's list. When the edition is not
specified, dwell on the pattern: the code has moved from dwelling units only toward any occupied
space where children are likely to be present. Knowing that dwelling units have been required
from the beginning, and that the expansion follows child-occupancy logic, handles most questions
without memorizing year-by-year changes.
Identifying a TR receptacle
Listed tamper-resistant receptacles are required to be marked "TR" on the face of the device.
That marking is mandated by the product listing standard (UL 498), not by the NEC text of
406.12 itself — what 406.12 requires is that the devices be listed tamper-resistant types.
In practice, an inspector verifies compliance at rough-in or trim-out by looking for the TR
marking on the face. Standard receptacles without that marking, even if they look identical,
do not comply in locations where 406.12 applies.
Functionally, a TR receptacle feels stiffer to plug into because the shutters require the
simultaneous pressure of both prongs to move. This is the same physical sensation for every
standard plug — a correctly operating TR receptacle accepts plugs normally; the slight
additional resistance is the shutters yielding to even pressure.
Replacements and existing installations
The NEC generally requires that where a receptacle is replaced in a location that requires
tamper-resistant protection under the edition in effect, the replacement device must also be
tamper-resistant. The intent is to prevent indefinite grandfathering — a receptacle that burns
out or fails in a dwelling is replaced with a TR unit as a matter of course, not as an upgrade.
This same principle appears alongside AFCI and GFCI
requirements: when you touch it, bring it up to current code. For the exam, the takeaway is that
TR is not limited to new construction; receptacle replacements in covered locations also trigger
the requirement. Knowing which locations are covered under the adopted edition, and that
replacement work is included, is the full scope of what the journeyman exam tests on this topic.