An expression is derived for the temperature rise of the
unexposed surface of a wall subjected to fire conditions on one side, the
unexposed face of the fire wall losing heat by Newtonian cooling to the
atmosphere. The limitations applying to the expression are discussed
and it is shown that the expression is valid provided the temperature
rise of the cooler surface is less than about half its equilibrium
value. Expressions are derived for the fire resistance time of a wall
subjected to a B.S. 476 furnace test.
