So many public restrooms use some automated febreeze sprayer to deal with the feces particulate odor in the room. If they used actual HEPA they could actually cut down on the particulate and odors without having the bathroom smell like you are inside a scented candle, or an Abercrombie store. Ongoing costs would probably be similar, HEPA filters are cheap just like a can of febreeze.
HEPA filters do not remove odors. Bad smell is caused by extremely small particles that cannot be removed by HEPA filters. To remove odor, you will need other filters, such as an activated carbon filter. Some air purifiers come with both a HEPA filter and a filter to remove odors.
