The suitability of ultraviolet (UV) radiation for the decontamination of a surgical face mask was studied by comparing experiments with ray-tracing optical simulations. The 3D fiber network was constructed from X-ray tomography images of the layered mask structure consisting of polypropylene fibers. Both simulations and optical measurements on reflection and transmission indicated that UV light was able to penetrate even the deepest material regions. The decontamination experiments, carried out using Staphylococcus aureus and MS2 microbes, indicated an over 6 log ₁₀ reduction in viable virus contamination of the inner filtering layer. This was achieved within two minutes at a moderate dosage level of 0.22 J/cm ². The simulations show that despite radiation reflection from the outer mask layer, a significant dosage enters the actual filtering layer due to multiple refraction and scattering of UV light from the inner fibers. This leads to an effective decontamination of fibers with small external UV dosage.