Abstract: A device including a housing that is substantially impermeable to ultraviolet radiation having a wavelength of from 280 nm to 400 nm, and at least one window defined in the housing, the window including a UV-C radiation band-pass mirror film having a multiplicity of alternating first and second optical layers collectively transmitting UV-C radiation at a wavelength from at least 100 nm to less than 280 nm and not transmitting UV-A and UV-B radiation at a wavelength of from 280 nm to 400 nm, and an ultraviolet radiation source positioned within the housing, the ultraviolet radiation source being capable of emitting ultraviolet radiation at one or more wavelength from 100 nm to 400 nm. The device optionally further includes an ultraviolet mirror film positioned within the housing so as to reflect ultraviolet radiation emitted by the ultraviolet radiation source. A method of disinfecting a material is also disclosed.