[en] Specific requirements pertaining to qualification of certain electric equipment important to safety are contained in Section 50.49, ''Environmental Qualification of Electric Equipment Important to Safety for Nuclear Power Plants,'' of 10 CFR Part 50. Section 50.49 requires that three categories of electric equipment important to safety be qualified for their application and specified performance and proves requirements for establishing environmental qualification methods for qualification parameters. These three categories are (1) safety-related electric equipment (Class 1E), (2) non-safety-related electric equipment (non-Class 1E) whose failure under postulated environmental conditions could prevent satisfactory accomplishment of safety functions by safety-related equipment, and (3) certain post accident monitoring equipment. This regulatory guide applies only to these three categories of electric equipment important to safety. Section 50.49 does not include requirements for seismic and dynamic qualification, protection of electric equipment against other natural phenomena and external events, and equipment located in a mild environment. This regulatory guide describes a method acceptable to the NRC staff for complying with Section 50.49 of 10 CFR Part 50 with regard to qualification of electric equipment important to safety for service in nuclear power plants to ensure that the equipment can perform its safety function during and after a design basis accident