If the dark matter of the Universe is made of sterile neutrinos with mass in the keV region, it can be searched for with the help of x-ray satellites. We discuss the prospects of laboratory experiments that can be competitive and complementary to space missions. We argue that the detailed study of β decays of tritium and other nuclei with the help of cold target recoil ion momentum spectroscopy can potentially enter into an interesting parameter range and even supersede the current astronomical bounds on the properties of the dark matter sterile neutrinos. © 2007 The American Physical Society.