The ratio of the window opening height to its width controls the shape of the plume. Tall windows tend to project flames away from the wall, decreasing the thermal coupling of the flames with the wall and causing relatively lower thermal exposure to it. Features that form vertical channels on a building facade, such as vertical shades or a recess in the facade, increase the hazard of high fire exposure to the facade. Features that disrupt vertical air movement along the facade, such as balconies, protect the facade above these features from high fire exposure. Certain combustible claddings can support unlimited vertical flame spread.
Testing is needed to evaluate flame spread propensity.
Smaller scale test methods, including the standard Steiner tunnel test, the IMO surface flammability test, and the modified roof deck test methods are not considered to be suitable for the assessment of flame spread propensity of combustible claddings. At this time, the full scale test seems to be an appropriate means to distinguish between acceptable and unacceptable combustible claddings. There is a good chance that a less expensive test can be developed. References MacDiarmid, H., Report on the fire commissioner's inquiry into the fire at 230 Fairlane Avenue, Winnipeg, Manitoba, on May 20, 1980. Ondrus, J. and O. Petterson, Fire hazards of facades with externally applied additional insulation.