They are certified free of PCR inhibitors, human DNA, RNase, DNase and pyrogens. Where swabs are marked as sterile this is by irradiation or EtO. Bioer Nasopharyngeal and Oral Swabs with Viral Nucleic Acid Sample Preservation Fluid not only protect the sample, but since the preservative rapidly inactivates the virus, the source of infection is removed to ensure the safety of healthcare staff.