Check your surge protector and you will most likely see marks from Underwriters Laboratories (UL), ANSI (American National Standards Institute) /IEEE (Institute of Electrical and Electronics Engineers) and IEC (International Electrotechnical Commission). These groups define standards for how products should functions as well as some also do testing and certification.
Check the surge protector for stamps from these groups in particular look for these codes:
- IEC 61643-1
- ANSI/IEEE C62.xx
- UL 1449
These indicate that the device is designed to function to specs for surge supression.
You cannot verify that the devices you buy actually perform to spec since the only way to actually test it is to push it to the point it fails, thus breaking the device. Good manufactures test random samples and verify that they meet the specs and so can make a good faith claim that the devices they sell will also meet the specs.