The time it lasts varies from person to person. For me it lasts about 10 months-others more and others less.
Jachymov is located near Karlovy Vary (Carlsbad) in Western Bohemia.
As far as I know, there aren't any radon facilities in France--just one in Austria and here in the CZ. Jachymov is the only place where the radon comes in contact with the skin through water--other places, like Austria or Montana, you go into a cave and breath in the gas.
Hope this makes sense--just got back from having a few Czech beers....
