Overview

As stated in ASTM E119, ^[105] standard furnace tests such as ASTME119; BS 476, Part 20 ^[106]; and ISO 834 ^[107] provide a relative measure of the fire test response of comparable assemblies under standardized fire exposure conditions. The exposure is not representative of all fire conditions because conditions vary with changes in the amount, nature, and distribution of fire loading; ventilation; compartment size and configuration; and thermal characteristics of the compartment. Real fires can be more or less severe in terms of duration, rate of heating, and peak temperature than the standard temperature time relationship in a furnace test.

Real fires are a function of fuel load, compartment dimensions, thermal properties of the compartment boundaries, and the quantity of unprotected openings that allow ventilation in a post-flashover fire.

Also of importance is that the standard furnace test does not assess real structural response in fire conditions because single elements of structure are tested in the furnace even though they form component parts of complex three-dimensional frames in real buildings.

Various methods exist for designers to derive more realistic temperature time relationships for compartments. For example, as a result of concerns with the standard furnace test temperature time relationship, work was carried out by Ingberg, Law, and Pettersson, among others, to determine what is known as an equivalent fire resistance. For these methods, the heating effect in a compartment is based on real compartment fire behavior and therefore takes into account fuel load density, ventilation openings, compartment dimensions, and...