I'll suspect the make chloramine filters for fresh water fish keepers that don't want to treat every gallon of water they use. Say like a breeder or a LFS
. Back before chloramines some twenty plus years ago I used photographic hypo to remove chlorine from fresh water at one drop per gallon in the aquarium. After the addition of chloramines I used two drops per gallon and treated the water before adding it to the aquarium. Where can I get a chloramine test kit for aquariums? I repaired a hot tub a long time ago!