Abstract: To provide an ultraviolet light irradiation device capable of inactivating bacteria, viruses, and the like with increased efficiency while ensuring safety. An ultraviolet light irradiation device according to the present invention includes a light source to emit ultraviolet light having a wavelength within a range of 190 nm or more and less than 240 nm, a housing to house the light source, a light extraction part to extract the ultraviolet light emitted from the light source out of the housing, and a diffusion transmission member to diffuse and transmit the ultraviolet light.

Abstract: An ultraviolet light irradiation device includes an optical filter. The optical filter has a transmission spectrum of zero-degree light including a first transmission band and a second transmission band that transmit the zero-degree light and a first restriction band that restricts transmission of the zero-degree light. The first transmission band is present within the wavelength band of 200 nm or more and less than 240 nm. The second transmission band is present within a wavelength band of more than 300 nm and less than 400 nm. The first restriction band is present over an entire wavelength range of at least 240 nm or more and 300 nm or less, and the first restriction band has an upper limit provided within a range of more than 300 nm and 380 nm or less.

Abstract: Provided is an ultraviolet light irradiation device that is capable of causing effective inactivation of microorganisms as well as a method of using the ultraviolet light irradiation device. An ultraviolet light irradiation device includes a light source that radiates ultraviolet light with a wavelength in a range of 190 nm to 235 nm; a housing that houses the light source; an extracting portion that extracts the ultraviolet light that is radiated from the light source and causes it to be directed toward an exterior of the housing; and a diffusing member that diffuses the ultraviolet light.

Abstract: The short-arc discharge lamp includes a pair of electrodes arranged facing each other inside a light-emitting tube, the pair of electrodes made of a material containing tungsten; a coating formed on the first outer surface of at least one of the pair of electrodes, the coating made of a material containing ceramics; and tungsten particles adhered to a part of the second outer surface of the coating.