Is it okay to use Hershey's Syrup without refrigerating it after opening?

It was downstairs in our pantry and since it's winter our basement is pretty chilly down there. It's probably been down there for a few weeks. It's full, but the seal was off so I'm guessing someone opened it. It smells perfectly fine, but I'm not positive about the taste. I'm not saying it tastes bad I'm just not sure what's bad and what's good. Do you think it'd be okay? How can I tell if it's bad?