For best AC accuracy HV clearances should be a radius equal to twice the height of the unshielded divider. HV withstand clearance should be at least 1 inch (2.54cm) for each 5KV to 10KV for DC or peak AC (RMS x 1.414), to nearest HV or ground. Maximum operating voltages are limited by voltage withstand of internal components, external flashover withstand and temperature rise limits of types with resistive components. On lower resistance units, steady state DC and PK AC may be limited to less than the rated peak short time operating voltage. For withstand test purposes, an impulse rating is also given to indicate the safety factor for transients above rated maximum operating PK voltage which could occur unintentionally. Flashovers may destroy attached measuring and display equipment and endanger personnel associated with it. Therefore safety factors must be observed.