Experiments have been conducted to establish temperature stratification conditions under which plume fluid from a fire source will or will not rise to the ceiling, and associated distributions of temperature rise and CO2concentrations. Small fire sources of heptane were used in a pre-stratified, insulated room. A critical, nondimensional, ambient temperature rise from the source level to the ceiling is associated with plume fluid just being able to penetrate to the ceiling, which turns out to be quite insensitive to the shape of the stratification profile, although the values are considerably higher than a value derivable from previous work of Mortonet al. Centerline behavior of temperature rise and CO2concentration agreed well with the theory of these authors up to the theoretical plume reach, but the experimental values needed an incremental height, roughly equal to 25 percent of the theoretical plume reach, to return to zero.