Influence of substrate on fire performance of wall lining materials

This study assessed the fire risk of attaching a qualified surface wall lining to an unqualified combustible substrate. Experimental materials were gypsum, magnesium oxide, calcium silicate board and fire-retardant plywood, which were attached to a non-fire-retardant plywood panel. The CNS 6532 Surface Test and the ISO 5660 Cone Calorimeter Test were applied. The former simulates the heating environment in the early fire stage and the latter simulates a fully developed fire. Experimental data show that when a qualified surface material was attached to a non-qualified substrate, the temperature rise in the Surface Test decreased. The substrates consequently enhance fire safety performance in the early stage of fire growth mainly due to crake prevention and a decrease in the amount of heat stored in surface materials for subsequent ignition. Additionally, the heat release rate in the Cone Calorimeter Test increased or decreased when a qualified surface material was attached to a non-qualified substrate. Therefore, the existence of substrates enhances or reduces a material’s combustibility rank when a fire is fully developed. The key mechanism is the crake or flame penetration of surface wall lining, which can lead to substrate ignition. The change of combustibility rank depends on the time at which a crake develops or flames penetrate a substrate.