They just don't want the item to go up in flames quickly. Such as those that can't be near an open flame or fabrics that melt quickly. A client of mine decades ago when I was a hairdresser was in the hospital and that was before smoking was prohibited, had a silky quilted bed jacket on. She fell asleep with the cigarette in her hand just as the nurse walked into her room. It burned the jacket but the quick thinking nurse grabbed the water glass and put the fire out. Things made of cotton are readily acceptable and most items brought in by family are taken home by family if they need laundered. It's the silky, satiny, nylon, polyester flimsy fabrics they don't welcome. I loaned my stepmother a warm Guess sweater (cotton) because she was always so chilly in the hospital for one stay. She took a nap with it on and when she woke up it was gone. Just make sure it's labeled so it doesn't come up missing!