What household items can emit radiation?
Smoke Detectors - Contain an Alpha and Beta ray producing radioactive isotope of the element Americium that senses smoke. This is sealed, though, and may not give you any reading.
Lantern Mantels - Some of the mantels in camping lanterns, especially those from earlier years, are made of the radioactive element Thorium. Be careful not to inhale the mantle ash!
Watches - Some old watches and clocks, even gyroscopes, have dials painted in radium to make them glow in the dark. Radium emits Alpha and Gamma rays. More recently, Tritium, a radioactive isotope of Hydrogen, has been used to paint the dials, but it is too weak to penetrate the watch lens.
Camera Lenses - It has been reported that certain old Leica camera lenses colored yellow owe their hue to the presence of the radioactive element, Thorium.
Jewellry - Certain gems are irradiated by the radioactive element Radium, X-rays, or other particles to produce a color change. This can make the gem itself radioactive which can last for years in some cases. Also, cloisonné, an enameled variety of jewelry, is glazed with Uranium oxide.
Rocks and Minerals - Minerals such as uraninite and its pitchblende variety, also carnotite and thorianite, contain the radioactive elements Uranium and/or Thorium.
Pottery - Some older pottery such as the Fiesta Ware brand often found in antique stores is glazed with Uranium oxide. When broken, the dust can emit Alpha particles of radiation.
Furniture - More recently, certain metal objects in the home are reported to be partly made of spent radioactive material.