Originally conceived as an apparatus to study near-limit flames and their breakup into flamelets and later modified to function as a microgravity simulation apparatus, the narrow channel apparatus serves also as a facility for examining long time flame spread and material flammability in on-earth (terrestrial) applications. These applications include flame spread in narrow gaps, persistence of flame in heat-loss environments, and flame-to-flamelet front transition. The narrow channel apparatus tests described here measure behavior of the spreading flame and features of the flame-to-flamelet transition. Measured quantities include flow, flame and flamelet velocities in normal and inverted tests, flow deceleration and acceleration rates with associated flame or flamelet response, flame-to-flamelet transition times, and influences of fuel thickness. The principal goal of this research was to ascertain the capacity of the narrow channel apparatus to produce data for phenomena observed in both (1) simulated microgravity flame spread and (2) terrestrial flame spread in narrow gaps and channels. Copyright © 2012 John Wiley & Sons, Ltd.