This part of IEC 62305 is applicable to risk management of a structure due to lightning flashes to earth. Its purpose is to provide a procedure for the evaluation of such a risk. Once an upper tolerable limit for the risk has been selected, this procedure allows the selection of appropriate protection measures to be adopted to reduce the risk to or below the tolerable limit. Risk management also includes the evaluation of frequency of damage of internal systems caused by surges due to lightning flashes to earth. Once an upper tolerable limit for the frequency of damage has been selected, this procedure allows the selection of appropriate protection measures to be adopted to reduce the frequency of damage to or below the tolerable limit.