The code in question would be 110.3(B)
You would need to use a product listed for this location.
The following is excerpted from UL's White Book section on Fans, Electric (GPWV)
"Ceiling-insert fans, wall-insert fans, and ceiling-insert fan/light combinations intended to be mounted over bathtubs, showers, or within the zone above the bathtub and shower area as defined by Article 410 of the NEC, are marked "Acceptable for use over a bathtub or shower when installed in a GFCI protected branch circuit." These products are investigated to determine the effects of moisture (dampness or wetting), such as shower spray."
You can find the entire text of (GPWV) athttp://database.ul.com/cgi-bin/XYV/templ...7360&sequence=1