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 a fire rated door if it has a louver and no louvers at all can be installed in a 3 hour rated door.
