The incident occured at 10:30 a.m., prompting police and firefighters to cordon off the sidewalk along the Fifth Street side of the 24-story building.
An hour later, officials closed off the street to pedestrians and traffic between N and O streets.
The glass panel fell from between the eighth and ninth floors of the 24-story building at 450 N St., said board spokesman Jaime Garza.
"No employees work there," Garza said, referring to the fact that the eighth floor is vacant right now.
The Department of General Services, which leases the building to BOE and is on the hook for fixing the problem, is investigating why the glass fell.
DGS has plenty of experience. Between 1999 and 2005, seven windows with faulty seals leaked water and fell to the street below. The department spent $15 million to fix the window system and millions of dollars more to remediate toxic mold, repair burst plumbing and fix faulty elevators.
BOE has said it wants to move, but legislation aimed at accomplishing that has stalled. SEIU Local 1000 recently organized an email campaign by rank-and-file BOE employees to raise awareness about the building's workplace hazards.
PHOTOS: The east side of the Board of Equalization Headquarters at 11 a.m. today (above) and a closeup shot of the spot between the eighth and ninth floors where a glass panel popped loose and fell to the sidewalk below. / Jon Ortiz, Sacramento Bee