Getting a crush on a coworker can be tricky because, as you pointed out, if it goes sour somehow it can mess with your work environment. So when you're weighing the pros and cons of telling him about your crush, you'll definitely want to consider what working around him would be like if he turns you down (you may also want to make sure your work doesn't have rules about employees dating each other). In a more general sense, this article has a lot of advice on how to navigate having a crush: Puppy Love: The Do's & Don'ts of Crushes (With Help from a Very Small Dog)
Too, something that can help with a crush is getting to know the person better. Do you feel like you know him pretty well, or are your interactions pretty limited?