Interior wall and ceiling finish materials shall be tested and accorded indices for flame spread and smoke development in accordance with ASTM E 84 or UL 723.
Such interior finish materials shall be grouped in the following flame spread classes in accordance with their flame spread index.
Class A: Flame spread 0‒25.
Class B: Flame spread 26‒75.
Class C: Flame spread 76‒200.
Class A: Flame spread 0‒25.
Class B: Flame spread 26‒75.
Class C: Flame spread 76‒200.
Interior wall and ceiling finish shall have a flame spread index not greater than that for the classification rating specified in Table 803.1 for the group and location designated.
Except where permitted for interior trim in Section 806.5, acceptable smoke-developed indices shall range from 0‒450 with the following restrictions:
| Exits, corridors | 25 or less |
| Occupancy Group I | 50 or less |
| Rooms in which the net floor area per occupant is 10 square feet or less | 100 or less |