Labeling is required for electronic products that emit ionizing radiation either by design (e.g., x-ray equipment) or as a consequence of operation (e.g., old cathode ray tube televisions).
No labeling is required for products that emit radiation due to decay of a radioactive element or isotope (e.g., ionization type smoke detectors).
For more information, see the Food and Drug Administration (FDA) page on Labeling Requirements for Radiation Emitting Devices and Products.