DougW hit it on the head. If your employees are using the "tool" for it's intended purpose, that's acceptable. If an OSHA officer says it's a violation, just ask them to quote chapter and verse. While some things may seem to be not quite right at first glance, if a standard cannot be cited, it is not a violation with the rare exception of the "standard duty clause" which is sometimes used as a catch-all.
Another exception (and this can be true of industrial goods as well as home use duty ones) would be if the worker mounts a fan (or radio, etc.) in even a semi-permanent manner and then uses a drop cord to power that unit. In that case (it might be a bit of a stretch, but I've seen it) a citation could be used for powering "equipment" with a drop cord.
Finally, if a drop cord is used, even temporarily, make sure it's not one of those dang flat (zip cord?) type that's a $0.99 item and Wal Mart. Those are almost never acceptable in a workplace...office type settings, you might get by with it.
