Anything that is susceptible to corpse impurity, even if it’s not susceptible to midras impurity, is susceptible to nega impurity. Examples include a ship’s sail, a curtain, the headband of a hairnet, the wrappers of scrolls, a girdle, and straps of shoes or sandals that are as wide as a split bean, All of these are susceptible to nega impurity. If a nega appears on a heavy coat, Rabbi Eliezer ben Yaakov says it’s not impure unless the nega appears on both the fabric and on its hairs. A waterskin and a leather wallet are inspected in their usual positions. A nega may spread from their interiors to their exteriors and vice versa.
If a garment that was quarantined got mixed up with others, they’re all ritually clean. If such a garment was cut up or made into stuffing, it’s ritually clean and one may derive benefit from it. However, if a garment that was confirmed as unclean got mixed up with others, they’re all ritually unclean. If it was cut up or made into stuffing, it remains unclean and one is not permitted to derive benefit from it.