This study examines an intervention aimed at improving the detection rates of closed circuit television (CCTV) operators during real-time surveillance. The intervention consists of electronically inserting graphic objects (IGOs) into video stream with the intention of assisting operators in detecting actual significant events. It is based on threat image projection (TIP) that has been used to heighten the performance of X-ray baggage screeners. Seventy-three participants observed a 90-min CCTV video from an industrial plant, showing both normal work activity and significant events. The control group received no IGOs, one treatment group received generic IGOs, and the second treatment group received IGOs with small semantic distances to target behaviours. There were indications that the IGOs had positive effects on alertness and attention sets, but this was not statistically significant. Reasons for this are discussed in terms of differences between the CCTV and baggage screening or TIP contexts.