AbstractA piston reactor has been developed to examine some aspects of particle formation during the pyrolysis of silane (SiH4). This reactor generates conditions intermediate between a static pyrolysis reactor and a shock tube reactor. It effectively excludes contributions of wall reactions to the pyrolysis experiments. The apparent kinetics for this reactor do not conform to values published in the literature. A model that incorporates silane‐particle reactions can account for the deviations. In addition, emission of visible light accompanies the sooting reactions. The source of this emission seems to be the sum of incandescence from the hot particles and continuum radiation from another source.