Special Product Characteristics:
These special product characteristics are derived from the DFMEA. The special product characteristic derived from the DFMEA are marked on the component drawings in form of notations. You normally will not have a characteristics at the system level drawings. Factors influencing the declaration of special product characteristic are:
1) Government regulation.
2) Safety concern.
3) Severety of failure mode
4) Occurances of causes.
Each organization has its way of nominating special characteristics. Some use charts like the one below to mark a feature as special characteristic.