Safe Clearances At Altitude

This calculator provides values of safe clearances required between air gaps at a specific altitude. The methodology used in the calculation is based on IEC 60664-1. A further adjustment is made for PWM voltages (where breakdown voltages may fall by 20%). If the clearance is also accompanied by an identical  creepage distance, you should note that this will generally set the safe distances in the gap (creepage distances fail at a lower voltage than the equivalent clearance).