Matt is 100% correct. There are no testing standards that are required to sell a helmet in the kayak industry. I can not say for sure what companies test their helmets, but I imagine all of them do.
I represent WRSI helmets and can say for sure that we are in the process of going throught the CE Standard testing. We will know the official results in the next few weeks. We have however done extensive testing in our factory as well as the now famous fire hose test that has caused much controversy. The Fire hose test was done at John Hopkins university and was used only to test the retention system we use in our helmets. The test helped us design a fit system that would keep the helmet from sliding back off the back of your head. In our factory we have done the impact tests to current written standards. We believe that our helmets have sufficiantly passed to our standards and we have now sent our helmets to a lab in the UK for official testing.
As Matt has stated though, these tests are essentially voluntary. They are not needed to sell helmets in the United States. If you have more questions about the helmet you use or are considering buying. I encourage you to call or write the company of interest and ask them what they do to make sure their helmets are safe for the sport you intend to use them for.
If you have anymore questions about WRSI helmets please check our website www.whitewaterhelmet.com
or email me at firstname.lastname@example.org