There are some basic requirements for an opening before it can be classified as fire rated:

The wall, frame, and door all have to be fire rated. The opening must be labeled at 2/3 of the wall rating. For instance, if you have a 90 minute wall, you must have a 60 minute label on your opening.

The door must be self closing. This is usually done by a door closer or, in some cases, spring hinges. Both serve the same purpose in that the door will close and serve it's purpose of holding back the fire.

The door must be self latching. Push and pull plates cannot be used on a fire rated door. The door has to latch into the frame when closed so it stays shut until it is manually opened. This means that you have to use at least a passage set on the door.

Steel ball bearing hinges must be used. Brass, bronze and other bases cannot be used. Steel based hinges are available in a variety of plated finishes.

As stated above, the purpose of a fire rated opening is to retard fire for a specific period of time. Most labeled doors will have an A, B, or C label:

A label: 3 hour rating. These doors are used for openings in walls separating buildings that are joined together. No glass is allowed in these doors.

B label: 1 1/2 hour rating. These doors are usually used for stairwell doors but are sometimes used at all the rated walls in a building. 100 square inches of exposed glass is allowed.

C label: 3/4 hour rating. These doors are used for openings from a corridor into another room in the same building. 1296 square inches of exposed glass is allowed.

Louvers can be installed on fire rated doors but they have to be fusible link. This means that once the heat from the fire reaches a certain temperature (usually 105 degrees), the fusible link will melt which causes the louver blades to close . This will help prevent the spread of fire. The maximum size for these louvers is 24 x 24. There is no glass allowed in the door if it has a louver.

Remember to follow the requirements listed above. Codes differ from area to area but these are the standard.