The request usually won't be _explicitly_ solicited, but there are other cues you can pick up on (ie flirting). Of course people can read general friendliness a

The request usually won't be _explicitly_ solicited, but there are other cues you can pick up on (ie flirting). Of course people can read general friendliness as romantic interest (or vice versa), but you can have at least a decent guess whether someone will be interested in going on a date with you. In some contexts it doesn't hurt to ask when you're unsure, but at work it's better to err on the side of caution (doubly so if there's any power difference between your positions).