How much clearance does the HP Z240 Tower Workstation need for proper ventilation?

The workstation requires at least 15.24 cm (6.00 in) of clearance at the front and back of the unit. You must also never restrict the incoming or outgoing airflow by blocking any vents or air intakes. Additionally, for Windows 10 setup, HP cautions that there must be a 10.2 cm (4 inch) clearance at the back of the unit and above the monitor to permit required airflow. (Pages 11, 32)