# Hazard study 4 Hazard study 4 is completed at the point of handover from the construction team to the commissioning team, and is designed to ensure that the plant has been installed correctly. These checks involve walking every line to check against the piping and instrumentation diagrams (P&IDs) that equipment has been installed in the correct locations and orientation, that joints have been fully tightened and that pipework is properly supported. The physical layout of the plant is also checked – for example making sure that valve handles are accessible and escape routes have not been blocked.