I tried to find the info on the wiki but it is difficult to find stuff there. When heroes do their "Exchange" phase, does that means they have to trade items? Or can a hero just give an item to another hero in their space? Logic would dictate the latter in my opinion, but I don't believe the rules are explicit enough about that.
You can give an item to another hero in your space without receiving anything in return. This FAQ from the back of the rule book clarifies this:
Q3. - If you have four items including Gasoline or Old Betsy, and you gain a fifth item, can you immediately use the Gasoline or Old Betsy to avoid having to discard an item?
A3. - Yes. You could also immediately hand off an item to any other Hero in your space.