What is the maximum flame spread index of foam plastic insulation used as an interior wall or ceiling finish?

The maximum flame spread index of foam plastic insulation used as an interior wall or ceiling finish is 75. This index is a critical measure in assessing how easily materials can ignite and promote the spread of flames in a building. In the context of building codes and safety, materials with a flame spread index of 75 or lower are classified as having a limited capacity to support combustion, making them suitable for certain applications in interior spaces as long as they meet additional fire protection criteria.

Materials with a flame spread index exceeding this value would typically indicate a higher risk of fire spread, which is why those standards are in place. Understanding the flame spread index helps inspectors assess fire safety measures in commercial buildings, ensuring compliance with local and national codes that aim to protect occupants and property.