The efficacies of three water-soluble fire retardant treatments and one fire retardant paint in preventing the smouldering of fibreboard have been studied. The treatments were applied to the surface of the board specimens and measurements were then made of the rates of smouldering in still air and under applied airflows. The amounts of water-soluble retardants to be added to the board to prevent sustained smouldering are sufficiently large to make application of the treatments difficult and also to alter the physical properties of the board. In practice, therefore, it may be simpler and more profitable to take other steps to prevent the initiation of smouldering in fibreboard, or to use other, less flammable, types of material.