When all new houses are being built you have to check to see if there is a risk for radon gas.
Most times if there is a risk all you have to do for new houses is provide a suitable polythene sheet within the ground floor which has to be sealed around any openings. If the risk is high then you have to have a fully ventilated void beneath the ground floor as well.
If you need radon protection for an existing house, this gives you the ways of doing it:-
Radon Centres Ltd - Radon Gas Testing