Gas holdup was measured at different locations in a 2.8 m(3) portable industrial scale subaeration flotation cell, treating zinc cleaner feed at Hellyer Concentrator in Tasmania, Australia. The cell was fitted in turn with four different impeller-stater systems, and operated over a range of airflow rates and impeller speeds. The gas holdup was found to increase with increase in impeller speed as well as with increase in airflow rate, the manner in which it increased depended on the impeller type. Values ranged from 2% to 33%, with the greatest values produced by the Outokumpu impeller.