Abstract: The current technical standards related to the safe service life of household appliances do not include the method of determining the safe useful life, which makes it difficult to implement the relevant standards. The safe useful life is the time when the safety is about to deteriorate significantly, and it is also the time node for the implementation of preventive maintenance. By analyzing the rule that the safety of household appliances decreases with the useful time, it is pointed out that the product safety problem affected by the use time is actually the reliability problem of safety-related parts. It is proposed to use the test method to use the fault density change data of critical parts to determine the safety function failure time, and then the preventive maintenance time is specified as half of the time when the safety function failure time begins.The method of determining the preventive maintenance time of household appliances is helpful to the effective implementation of the standards related to the safe useful life of household appliances.

Key words: Household appliances, Preventive maintenance, Useful life, Critical parts, Durability, Safety, Reliability, Test