Actually, I do know what it smells like. In my first year labs, on of the things we had to do was examine drosophila (fruit flies) for certain traits. To do that, we knocked them out with chloroform and then looked at them under a low-power microscope. As a gas tends to do, some of it escaped when we opened the lid. Obviously, there wasn't enough to knock a person out, but if you breathed in enough it'd give you a killer headache