People tend to check in during these times:
Purnell is home to the Exelon Trading Center, a 2,200-square-foot center containing 16 classroom workstations, four research room workstations and real time feeds to two tickers and four LCD displays.
First floor classrooms are good. 2nd and 3rd floor rooms are less good.
The floors in the classrooms on the second and third floors are always filthy. Try to keep your stuff off them.
After 5pm the Central lot @ the Blue & Gold club across from Purnell becomes open to all passes.
There is usually free food almost everyday around lunch time from whatever company is visiting for the day.