Should I ask out a coworker?

I was told years ago not to "fish" in a company pond, I broke the rules on many occassions and it has always been a diaster.

Unless this is the person of your dream and you never break up with them, it is ok, but if you ever break up your working relationship will never be the same

Very true, things could get weird at work afterwards. But if this is just a part time job and you really want to see where it could go, go for it. If things don't work out and work gets weird look for a new job.

I agree, if it a part time job, things are sdimplified for you.If its your regular job do some brainstorming.
Depends on how much you want to take the risk, and I would love to know what your risk assesment came to, because for one you should know that if things don't turn out well in the long run, and you have to see each after that could you be able to handle that.
Just a few points you should put down while thinking of asking him out, are

From your communications with him, what is the most probable answer that he will give.. A yes or no.
If he does give the yes, can you handle the what next....
To play it safe , I think you should consider doing a group office outing, test the waters before you take the deep! And give it time, his mind might be going through the same querries

Their are better places to find some one, and safer too, as you never know when a relationship will affect your job status. A bad date could get one of you fired then what?