A sudden change in temperature. Thermal shock test; The resistors shall then be mounted on a rack of low-heat conducting material, and rated power shall be applied until thermal stability has been reached. The power shall then be removed and within 8 seconds to 12 seconds, the resistors shall be subjected to an air temperature of -55OC +0OC, -5OC for a period of not less than 15 minutes. Measurement of resistance shall be made not less than 2 hours after final exposure.