Equipment, which uses zinc oxide components such as ZNRs and varistors between the line
voltage and ground or between the lines of opposite polarity in the power supply circuit having a hazardous voltage and capable of delivering power exceeding 15 W continuously for at least 5 seconds, shall incorporate protective means against the occurrence of short-circuit failure (including semi-short circuit) in those zinc oxide components, in order to prevent smoke emission, ignition and fire hazards.