"Business casual" is one of those terms which takes in an awful lot of ground. It can mean anything from "your jeans should be reasonably clean" to "a pale blue shirt and/or a conservative sport coat may be substituted for the standard white shirt and grey or navy suit."
Is it common and accepted practice for the people in your business casual workplace to wear chinos? If so, then I'd say chinos are appropriate for your office's version of business casual.
Yeah, our workplace is pretty flexible. You can come in wearing a suit if you want everyday, or you can opt to wear chinos + dress shirt. Really, the only time it's mandatory for us to wear a suit is when we have clients coming over. So I guess I sort of answered my own question. I think I was more confused on the difference of chinos or khakis like some posted here. I just started hearing the word "chinos" a few years ago, and it was by celebrities who would wear them in weird colors.
I personally like to alternate depending on my mood (and how late I'm running).