In response to a question I received today ...
Prayer is one of the required elements of Islam. (http://encarta.msn.com/encyclopedia_761579171_2/islam.html).
There is a short window of time during which the evening prayer may be done. This time changes slightly each day, according to the length of the day, and according to the location. (See http://www.islamicity.com/PrayerTimes/ for a daily time calculator for any location worldwide.) Currently, the sunset prayer in Columbus should be performed at 8:10 p.m.
The length of time of the "window" during which a Muslim may pray appears to vary somewhat according to sect, although I haven't been able to clarify this completely. I have been told by one Muslim that there is a 45-minute window; another told me there is a 10-minute window. The prayer itself should take about 10 minutes.
The most reasonable accommodation, in my view, would be to provide a room where the Muslims could pray out of sight of others. This could be a meeting room or some other room not in use at the time. The employees would also need to have the opportunity to perform ritual washing (wudu) before prayer if that is needed. (http://www.geocities.com/rameezabid/wudu.htm) If washing is needed, that would require a few extra minutes.
However, this is only my opinion, based on experience and research. For legal requirements and any recent findings regarding accommodations for prayer in the workplace, I recommend that you contact your company's attorney.