AbstractAn apparatus based on the BS 476 Part 7 small scale flame‐spread specification, which has evolved over a number of years, is described. Many changes from the original simple gas/air furnace have been introduced, which have led to the development of a very useful flame‐spread test apparatus where all known variables are precisely controlled. The work has shown that the radiometers described in the standard do not monitor all the variables which affect flame‐spread results, and reported problems of reproducibility and variation on the large scale test, may be due to inadequate control of the furnace. The significance of the results is that the use of gas/air radian panels as the basis for flame‐spread tests needs to be re‐examined. All parameters should be carefully controlled and the entire procedure, particularly regarding the use of pilot ignition sources, needs to be reconsidered. There is an increasing need for test methods which assess materials at radiation intensities beyond that given by small ignition sources. The type of flame‐spread apparatus described in the paper may help fulfil this important