For functional and safety purposes, many fire doors will need to have glazing, in the form of vision panels. NFPA 80, Standard for Fire Doors and Other Opening Protectives, regulates the size of the glazing allowed in these applications in Table 4.4.5. The limitation on the size of the glazing is based upon the fire protection rating of the door. Fire doors with the highest fire protection rating, often limited in their application, are restricted to the smallest amount of glazing that can be in the door leaf.
For the most part, the size of the fire protection glazing is limited to the sized tested by the laboratory and meeting the appropriate test criteria for the doors and glazing installations. Doors with a 3 hour fire protection rating are limited to 100 sq. in.
Doors containing fire resistance–rated glazing materials fabricated and tested as door assemblies in accordance with NFPA 252, Standard Methods of Fire Tests of Door Assemblies, to determine a fire protection rating should be regulated by this standard as a fire door assembly and not as a glazing material permitted in fire door assemblies as prescribed in Section 4.4. Regarding Table 4.4.5, footnote c, consideration should be given to limiting fire protection glazing size in non–temperature rise doors where 60- and 90-minute fire protection is required due to radiant heat hazards.
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