http://etlwhidirectory.etlsemko.com/WebClients/ITS/DLP/products.nsf/$$Search?OpenForm[/url]
ETL (Electronic Testing Laboratories?) is one of the test organizations that covers spas; another is UL (Underwriters Laboratories). CSA (Canadian Standards Association) I believe may cover some of the electronic components used in spas. TUV is the standard in Europe. There are many more.
Please do search with some care. If you were to look for Arctic Spas, for example, you'd find no results. What?!! Aren't they ETL listed?
Ah, but wait! A search for Blue Falls Manufacturing, the parent company to the brand, turned up the various ETL listings for Arctic Spas and Coyote Spas and other products.
You can also check for TUV (European certification for exported spas). There are numerous TUV testers and sites; our certificates are logged at
http://www.tuev-sued.de/ TUV SUD . I was able to find them easily with the Certificate Explorer - but if you were searching a different TUV organization, you might miss them -- and again, search for Blue Falls Manufacturing.