This Bulletin describes two methods for designing the fire protection of aluminum structure in ships, the traditional "A", "B", "C" Class system, and a new approach which bases protection on the fire exposure.
The Bulletin is based on a series of fire tests conducted at the National Bureau of Standards from 1968 to 1970. These tests established the amount of insulation needed to protect the aluminum structure for various lengths of time under a standard fire exposure.
They showed that insulation on the fire exposed side of the structure is necessary to prevent melting or weakening of the aluminum, but that insulation on the unexposed side is harmful because it raises the temperature of the metal. The results of these tests have been used to develop formulas, tables, sketches, and sample calculations which are included to make the bulletin a working tool in the design of the shipboard aluminum structure.