Is it safe to place the HP EliteBook 8460p on my lap while using it?

No, HP warns against placing the computer directly on your lap or obstructing the computer air vents to reduce the possibility of heat-related injuries or overheating. You should use the computer only on a hard, flat surface. Soft surfaces such as pillows, rugs, or clothing should not block airflow, and the AC adapter should not contact skin or soft surfaces during operation. (Page 3)