In the 2010 edition of NFPA 80 – Standard for Fire Doors and Other Opening Protectives, a requirement was added stating that glazing materials in vision panels in new wood doors must be installed in accordance with inspection service procedures and under label service (paragraph 220.127.116.11). The explanatory paragraph in Annex A (A.18.104.22.168) clarified that new wood fire doors are required to have the glazing and light kits installed at the door manufacturer, or under label service (ie. in a wood door shop approved to modify fire doors).
This requirement has not changed in the 2013 or 2016 editions of NFPA 80, and the NFPA 80-2016 Handbook explains why this requirement was added – it is difficult or impossible for inspectors to determine in the field whether all installation standards were met, and clips and other specialized installations used for vision panels on wood fire doors can’t be verified in the field. Because of these difficulties specific to wood doors, glazing must be installed and shipped with the door. This requirement for glazing installed at the factory or in an authorized shop does not apply to hollow metal doors.