This standard specifies a uniform method for determining the flash point of plasticizer products using the Cleveland open-cup apparatus. The test involves placing the sample into a metal cup of specific dimensions (Cleveland cup) and heating it at a constant rate under standardized conditions. The lowest temperature at which the vapor of the sample momentarily ignites upon contact with a test flame at the cup's opening is recorded as the flash point. The key instrument for performing this test is the Cleveland open-cup flash point tester. Modern fully automatic flash point testers typically integrate heating control, ignition devices, and highly sensitive flame detection units, enabling the automated execution of the entire process, including heating, scanning, result determination, and atmospheric pressure correction. This method provides an essential standard basis for evaluating the safety of plasticizers during storage and transportation.