You ask very correct questions, so that linen bugs do not start in the hostel, you need to clean the mattresses. Many students seek advice and instructions https://www.fortador-usa.com/blog/how-to-steam-clean-a-mattress-to-remove-urine-sweat-stains-dust-mites and can you steam clean a mattress with a steam cleaner. This is a simple procedure - first you need to vacuum it and preferably treat it with soda, then go through the steam cleaner and let it dry for more than 24 hours.