Abstract: A sanitizer uses a radiant energy source such as a microwave source to excite a gas contained in a bulb so that the gas produces ultraviolet radiation that can be used to sanitize substances exposed to the radiation. The ultraviolet radiation may also be used to generate ozone from oxygen in air or another gas containing oxygen and the ozone may be used by itself or in combination with ultraviolet exposure to sanitize substances. The bulb for generating ultraviolet radiation can be shaped so that substances to be sterilized are able to pass through the bulb, so that objects (even metal objects) are enclosed by the bulb and shielded from the radiant energy source, or so that the bulb is located at the end of a waveguide and can be positioned to sanitize inaccessible surfaces or substances.