What is the maximum glass light size on a 3 hour (180 minute) fire rated door?

Maximum glass light sizes for 3 hour fire doors is as follows:

1. Wire glass - not approved for use in 3 hour fire doors.
2. Ceramic glass:
• UL & ITS/WH allow one (1) light with 100 square inches (.06 square meters) maximum of glass is permitted on 3 hour
• Maximum width of 12" (305 mm) or height of 33" (838 mm).
• L, B, & T series doors if Firelite or other 3 hour listed glazing material is used.
3. Some local building codes do not recognize the use of glass lights in 3 hour fire doors:
• Historically, a 3 hour fire door could not include a glass light.
• Recent code changes and fire tests have allowed for the use of listed glass lights designs:

Multiple glass lights are not allowed on 3 hour fire doors.