This paper presents and discusses some scaling laws which have to be considered within the framework of fire-induced smoke simulation using a buoyant release at lower scale. The correspondences between the fire and the buoyant release are supposed known and then, for a size reduction, dimensionless numbers are obtained from the buoyant jet momentum equation. It then appears, theoretically, that the single Froude similitude used in many laboratory experiments is inadequate for fire problems when the Boussinesq approximation cannot be considered. Indeed, in that case, the density difference between the released fluid and the ambient fluid has to be the same for both full and reduced scales. An alternative theoretical justification is also proposed from considerations on the source parameter Gi.