Mass flow rate through a horizontal opening at small pressure differences

The smoke and air flow through a horizontal opening was investigated using model-scale room equipped with on the ceiling. A layer created under ceiling small gas burner. pressure difference across changed by controlling supply to exhaust from space above opening. Smoke patterns were either downward uni-directional of air, bi-directional or upward. By changing opening, critical differences cause determined. It found that 0.98 buoyancy for onset upward flow, 0.47 flow. From measured carbon dioxide concentration, mass rates calculated correlated non-dimensional in case flows.