If you have ever shared a room with multiple people for days on end, you may know how clothes and living conditions can rapidly turn rather smelly. Imagine that happening in a confined spacecraft.
Even worse, since water on a space mission is in short supply, space travelers can't easily do their laundry. This is more than a body odor problem — unclean clothes and linens are ripe feeding grounds for infectious bacteria. Astronauts might wear the same clothes for days or even weeks, seal away used clothes in airtight bags, then return them to Earth for cleaning or cast them away to burn up in Earth's atmosphere.
