What are the requirements for lights and receptacles in fire rated ceilings (residential)? I have heard about special "dome" like covers for recessed fixtures and two hour rating for plastic boxes, but what else do I need to know? Thanks!
Welcome to the forum.
As others have already stated the fire resistance requirements come from the building codes and not the NEC.
For dwelling units that are stacked on top of one another the floor ceiling assembly will be required to have a fire resistance rating to create a "Unit separation" to separate the 2 dwelling units. The floor ceiling assmembly may on be penetrated by listed membrane or through penetrations depending if the opening goes all the way through the floor ceiling or just through the ceiling part.
For recessed cans penetrating this floor ceiling assembly there are a few options. You can box around the recessed can housing with sheetrock the equivalent of what the rest of the ceiling is made of, or you can use a fire rated can or rated dome cover or other listed product to maintain the required fire rating.
Most plastic boxes have a fire rating for both the wall and the ceiling so as long as the box has the required fire rating for the ceiling you can use the box without any other material.
Chris