An effect due to heat sources within a local exhaust enclosure (stack) producing convective air currents with vertical velocities proportional to the rate of heat transferred to the surrounding air and to the height of rise of the heated air. When hot gases rise through a stack, the vertical stack exit velocity is proportional to the square root of the difference in the densities of the heated air column and that of an equal column of the surrounding ambient air.
Air, as in a chimney, that moves upward because it is warmer than the ambient atmosphere.
A condition resulting from the rise of heated air, which creates positive pressure near the top of the building and negative pressure toward the bottom. Stack effect pressures have been known to overpower mechanical ventilation systems, disrupting proper circulation and contributing to the infiltration and stagnation of pollutants.