What are the flame spread categories and their index ranges?

What are the flame spread categories and their index ranges?

• A. Class S: 0-30; Class M: 31-80; Class L: 81-150
• B. Class A: 0-25; Class B: 26-75; Class C: 76-200
• C. Class A: 0-30; Class B: 31-100; Class C: 101-250
• D. Class D: 0-15; Class E: 16-60; Class F: 61-120

Answer: (B)

Flame spread is rated by an index that shows how quickly flames travel along a material’s surface, and materials are grouped into three categories from the least to the most flame spread. The standard ranges are Class A for 0–25, Class B for 26–75, and Class C for 76–200. This arrangement places the lowest values with the least spread (Class A) and the highest values with more rapid spread (Class C), making it easy to compare materials at a glance and apply in early fire assessments or code considerations. Other option sets either mix different letter labels or assign ranges outside these three categories, so they don’t align with the common three-tier system used here.

Flame spread is rated by an index that shows how quickly flames travel along a material’s surface, and materials are grouped into three categories from the least to the most flame spread. The standard ranges are Class A for 0–25, Class B for 26–75, and Class C for 76–200. This arrangement places the lowest values with the least spread (Class A) and the highest values with more rapid spread (Class C), making it easy to compare materials at a glance and apply in early fire assessments or code considerations. Other option sets either mix different letter labels or assign ranges outside these three categories, so they don’t align with the common three-tier system used here.