Gregory Klein Schneider, Autoclaving cardboard tubes, such as those from paper towel rolls, is a commonly used method for sterilising environmental enrichment items for mice, but it must be done with care. While some sources warn about fire risks, autoclaving is generally safe if the tubes are clean, dry, free of adhesives or inks, and placed in autoclave-safe bags or containers to prevent direct contact with heating elements. Using a standard gravity cycle at 121°C for 15–20 minutes is typically sufficient; however, it's essential to ensure proper drying to prevent sogginess or mould growth. Tubes should be spaced to allow steam penetration and fully cooled before use. Although rare, overheating or contaminated tubes could pose a fire risk, so it's essential to follow your institution's safety protocols. Alternatives such as gamma irradiation, dry heat, or purchasing pre-sterilised enrichment items may also be considered; however, UV treatment is generally ineffective for porous materials like cardboard. If allowed by your facility, autoclaving remains a practical and effective method for sterilising cardboard enrichment, provided it’s done with appropriate precautions.

Dry heat seems fitting for this. Try the oven overnight at 120 °C.

Fire - autoclaving?? That is absurd. Where do you read this?

UV does not sterilize.

Dry heat sterilization - 160 °C (320 °F) for 2 hours or 170 °C (340 °F).

But do you need actual sterilization? What risk are you trying to eliminate?