Equipment can be electrically correct and still be wrong for the environment where it is installed. Article 100 helps define the location before equipment, enclosures, wiring methods, and fittings are selected.
Dry location
A location not normally subject to dampness or wetness. Temporary moisture does not automatically make a location damp or wet.
Damp location
Protected from weather and not subject to saturation, but exposed to moderate moisture. Covered exterior areas, sheltered spaces, locations with moisture but no saturation.
Wet location
A location subject to saturation with water or other liquids, including unprotected areas exposed to weather. It also includes certain underground or earth-contact installations. Water exposure is expected, not incidental.
Rainproof, raintight, weatherproof, watertight
These terms describe different types of environmental protection. They are not interchangeable. The required protection depends on the actual exposure and applicable NEC requirement.
MEP coordination
Rooftop HVAC equipment, exterior disconnects, cooling towers, pump installations, washdown areas, mechanical yards, below-grade equipment, condensation-prone locations. The question is not only “will it fit here?” It is also “is it suitable for this environment?”
Do / Don’t
Do classify the location before selecting equipment, verify enclosure suitability, coordinate rain/moisture/condensation/washdown, review nameplates, and verify existing outdoor equipment before reuse. Don’t assume “outdoor rated” answers every question, treat damp and wet as interchangeable, assume a covered exterior location is dry, ignore condensation around mechanical equipment, or reuse an enclosure without confirming its rating.
Field tip
For exterior or mechanical equipment ask: direct rain? Water spray or accumulation? Expected condensation? What enclosure rating is provided? Environmental suitability should be resolved during design, not at inspection. Hub: dry / damp / wet. This completes the 12-part Article 100 must-know definitions series. Next: Article 110.
Code basis and professional boundary
NEC 2026 Article 100 terminology education from the owner-provided Daily Code Talk source. Confirm adopted edition, amendments, listings, and AHJ path. Not an enclosure selection.