ARE THERE ANY MATERIALS THAT CAN BE PENETRATED BY UV-C RAYS?

There are very few materials that will not block the passage of the germicidal wavelength (253.7 nm, invisible), including quartz and certain plastics such as PE or tetrafluoro-derivatives, but only if these are just a few microbes thick.
Regular window glass, polycarbonate and other transparent materials through which it is possible to see the bluish light of UV-C lights completely nullify their germicidal effect, acting as a screen.

Warning: Our UVC products must be used as directed and can pose health and safety risks.