Question:
As per the National Building Code of India 2016, the minimum fire resistance of service ducts and shafts is minutes.
As per the National Building Code of India 2016, the minimum fire resistance of service ducts and shafts is minutes.
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NBC 2016 treats service shafts as a fire-spread risk between floors and fixes their minimum fire resistance rating at 120 minutes (2 hours).
Updated On: Jul 16, 2026
- 45
- 60
- 120
- 240
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Verified By Collegedunia
The Correct Option is C
Solution and Explanation
Step 1: Understanding the Question:
The question asks for the minimum fire resistance rating, in minutes, that the National Building Code of India (NBC) 2016 requires for service ducts and shafts, meaning the vertical or horizontal enclosures that carry building services like electrical risers, plumbing, or ventilation between floors.
Step 2: Key Concept or Approach:
Fire resistance rating is the length of time a building element can hold back fire, heat, and structural collapse under standard fire test conditions, expressed in minutes or hours. Service shafts are treated as critical fire-safety elements because an unprotected shaft can let fire and smoke travel quickly between floors, so codes set a specific minimum rating for the enclosing walls of such shafts.
Step 3: Detailed Explanation:
As per NBC 2016 (Part 4, Fire and Life Safety), the minimum fire resistance rating specified for service ducts and shafts is 120 minutes, that is, 2 hours. This value is set high because a lift shaft, electrical duct, or similar vertical service shaft, if breached, becomes a direct path for fire to spread floor to floor, so the code demands a stronger enclosure than for many ordinary internal partitions. The lower values, 45 and 60 minutes, are typical ratings used for other elements like some doors or partitions with lighter fire-safety demands, not for service shafts; 240 minutes is higher than what the code actually specifies for this particular element and belongs to some higher-hazard structural situations instead.
Step 4: Final Answer:
The minimum fire resistance of service ducts and shafts as per NBC 2016 is 120 minutes.
The question asks for the minimum fire resistance rating, in minutes, that the National Building Code of India (NBC) 2016 requires for service ducts and shafts, meaning the vertical or horizontal enclosures that carry building services like electrical risers, plumbing, or ventilation between floors.
Step 2: Key Concept or Approach:
Fire resistance rating is the length of time a building element can hold back fire, heat, and structural collapse under standard fire test conditions, expressed in minutes or hours. Service shafts are treated as critical fire-safety elements because an unprotected shaft can let fire and smoke travel quickly between floors, so codes set a specific minimum rating for the enclosing walls of such shafts.
Step 3: Detailed Explanation:
As per NBC 2016 (Part 4, Fire and Life Safety), the minimum fire resistance rating specified for service ducts and shafts is 120 minutes, that is, 2 hours. This value is set high because a lift shaft, electrical duct, or similar vertical service shaft, if breached, becomes a direct path for fire to spread floor to floor, so the code demands a stronger enclosure than for many ordinary internal partitions. The lower values, 45 and 60 minutes, are typical ratings used for other elements like some doors or partitions with lighter fire-safety demands, not for service shafts; 240 minutes is higher than what the code actually specifies for this particular element and belongs to some higher-hazard structural situations instead.
Step 4: Final Answer:
The minimum fire resistance of service ducts and shafts as per NBC 2016 is 120 minutes.
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