While it’s generally safe to use an exterior light fixture indoors, the reverse isn’t true. You should not use an indoor light fixture outdoors in wet locations. They aren’t sealed against moisture and will stop working during the first heavy rain. Moreover, they aren’t corrosion resistant and could become an electrocution hazard if the parts that cover the electrical connections deteriorate. However, you may be able to use certain interior fixtures, which are UL-rated as “damp,” in covered porches or other covered outdoor areas that are shielded from the elements.
Here is how to know what is what – All lamps and lighting fixtures sold in the United States are required to be tested and rated by an independent product safety certification organization, such as Underwriters Laboratories (UL) and carry a product safety approval mark for dry, damp, or wet locations.
UL Listed (for Dry Locations)
Often noted just as “UL Listed.” A dry location is an indoor area that is not normally subject to dampness. It may include a location subject to temporary dampness provided ventilation is adequate to prevent any accumulation of moisture.
Dry Locations include kitchens, living rooms, dining rooms, bedrooms, foyers and hallways.
UL Listed for Damp Locations
Only lighting fixtures “Suitable for Damp Locations” or “Suitable for Wet Locations” can be used in damp locations. A damp location is an exterior or interior location that is normally or periodically subject to condensation of moisture in, on or adjacent to the electrical components of a lighting fixture.
Indoor Damp Locations include bathrooms, indoor pools and utility rooms.
Outdoor Damp Locations include covered patios and covered porches that are fully protected from water, even during storms.
UL Listed for Wet Locations
Only lighting marked “Suitable for Wet Locations” can be used in wet locations, both indoors and outdoors. A wet location is an interior or exterior location in which water or other liquids may drip, splash or flow on or against the electrical components of a lighting fixture or ceiling fan.
Outdoor Wet Locations include open-air decks and patios, uncovered porches, outdoor dining areas, exterior walls, gazebos, pergolas and walkways.