RESPONSE TO COMMENTS BY CHEW ET AL.

Having received the comments by Chew in relation to my own comments on their work and discussed them informally with a collaborator, I have the following to add. The terms ‘flaming ignition’ and ‘smouldering ignition’ used by them are open to criticism: it is propagation, which follows combustion, which is either flaming or smouldering, and a smouldering-to-flaming transition is possible (indeed, frequently observed) long after ignition [1]. In fairness to Chew et al. I will add that the terms smouldering ignition and glowing ignition have been used to a limited degree in the literature, but the two expressions are not necessarily synonymous as Chew et al. say they are. Smouldering is frequently accompanied by absence of any radiation emission in the visible region, as I myself observed in an experimental programme a good number of years ago [2,3]. Propagation rates were those expected for smouldering and there was abundant smoke but, in most if not all of the large number of experimental tests carried out, no visible glow at the propagating front. So to assert equivalence of smouldering and glowing behaviour is on these grounds open to question.