The required fire protection rating for an opening protective, such as a fire door assembly, is determined by the rating of the fire barrier in which it is installed. According to NFPA 101, Life Safety Code, a 2-hour rated fire barrier requires a fire door assembly with a minimum rating of 1-1/2 hours. This difference in rating accounts for the fact that the entire wall is not expected to be subjected to the full fire exposure simultaneously, and the door assembly's performance is evaluated based on its ability to limit temperature rise and prevent the passage of flame for a specified period, which is deemed sufficient to maintain the integrity of the compartment.

A. 45 minutes: This rating is insufficient for a 2-hour fire barrier and is typically associated with 1-hour rated barriers or smoke barriers.

B. 1-hour: This rating is also insufficient for a 2-hour fire barrier; it is generally the requirement for openings in 1-hour rated vertical shafts or barriers.

D. 2-hours: While a 2-hour door would be permitted, it is not the minimum required rating as specified by the code for this application.

1. NFPA 101, Life Safety Code, 2021 Edition, Table 8.3.4.2, "Fire Door and Fire Window Assembly Ratings for Fire Barriers." This table explicitly lists "1-1/2 hr" as the "Minimum Fire Protection Rating of Fire Door Assembly" for a "Fire Barrier Rating" of "2 hr."

2. NFPA 80, Standard for Fire Doors and Other Opening Protectives, 2019 Edition, Annex A, Table A.4.2.1, "Typical Fire Door Ratings for Fire-Rated Walls." This table provides guidance consistent with NFPA 101, showing a 1-1/2 hour (90-minute) door is typically used in a 2-hour wall.

3. SFPE, Handbook of Fire Protection Engineering, 5th Edition, Springer, New York, NY, 2016, Chapter 53, "Fire Resistance of Structural Assemblies," Section 53.5.2, pp. 1868-1869. This section discusses the principles of opening protection, noting that door ratings are typically less than the wall rating in which they are installed. (DOI: https://doi.org/10.1007/978-1-4939-2562-453)