A breakstem rivet installation tool includes an airflow ejector for ejecting broken-off stems through a rear pipe (23) mounted on the tool housing (11). The ejector is provided by the annular gap (28) between the front-end of the rear pipe (23) and the rear-end part (26) of an extension pipe (25) mounted on the reciprocable stem-pulling draw rod (13). In order to adjust the rate of air-flow through the ejector, the rear pipe (23) is axially adjustable to vary the size of the annular gap (28). To this end, the pipe (23) is screw-threaded into the housing, and its position can be locked by a lock nut (62). The range of adjustment of the ejector flow includes complete shutting off the air flow.