The Backrooms

Worn Sacks are known to be made with special convective currents, allowing them circulate air at a rate being breathable. Due to this, you are able to stay in a Worn Sack for around 1 hour before experiencing hypoxia. The walls inside of a Worn Sack, as well as the floor, resemble the material of the Worn Sack itself. This means if a bag is made of textile covering, the entirety of the inside of a Worn Sack will be made of textile covering. To exit, just imagine an exit, and leave, you will appear right next to the spot where you last placed your Worn Sack, with it on your back.

This was already covered in the page. But it's possible that it wasn't at the time of your post, or that you accidentally skimmed over it. Either way, even though entering it is possible and safe for about one hour, sleeping in it may not be the best idea.