Superficial gas velocity was measured at different locations in a 2.8m(3) portable industrial scale sub-aeration flotation cell, treating zinc cleaner feed at Hellyer Concentrator in Tasmania, Australia. The cell was fitted in turn with four different impeller-stator systems, and operated over a range of air flow rates and impeller speeds. Superficial gas velocity values ranged from 0.29 cm/sec to 6.4 cm/sec at the airflow rates employed. The distribution of air in the cell was very dependent on the impeller type, as well as on the operating conditions in the cell. For a well dispersed condition, the value of superficial gas velocity was uniform at different locations, whereas for flooding conditions the superficial gas velocity was very high near to the impeller and much lower away from the impeller.