A heat-delivery apparatus (12) heats a heat-shrinkable sleeve (10) on a pipe (2). The heat-delivery apparatus (12) includes one or more heater elements (20) which define an interior heating surface that surrounds the sleeve (10). An air space is thus defined between the exterior of the sleeve (10) and the interior heating surface. The flow of air, that would otherwise be generated by the step of applying heat, within said air space is controlled or restricted for example by means of fins (50, 50s, 60) that control or restrict the airflow, fully or partially sealing the air space with one or more sealing members (70), or fans (80) that generate an opposing airflow (82).