It will be business as usual at the D.C. Municipal Center today - if 2,000 police and city government employes find the atmosphere to their liking.

For the second time since a tear gas explosion drove employes, coughing and crying, into the streets 2 1/2 weeks ago, the building, at 300 Indiana Ave. NW, has been declared officially habitable.

All its offices were to be open today, and all employes will be expected to work their usual eight-hour shifts, according to a police spokesman.

But if employes are uncomfortable, shifts could be cut back to four hours, the spokesman added.

Sam D. Starobin, the city's director of general services, originally predicted that five days of airing out would be sufficient to rid the building of the gas.

Police officials were skeptical. "Tear gas is a powder initially," said Sgt. Richard Lamb, "and when it explodes it becomes a powder again. You can't get it out with just ventilation."

The first scheduled reopening, on Tuesday, Jan. 17, was abandoned by popular consensus after a few melancholy hours. Despite open windows and the widespread use of gas masks, employes could not keep from cyring. Some sought medical attention. Others went home.

A day later, Mayor Washington appointed a 10-man task force to size up the problem and outline its solution. A spokesman for the mayor was quick to lay the blame elsewhere.

"The situation was Mr. Starobin's responsibility," said Sam Eastman of the D. C. government's public information office. "In hindsight, whether he should have sought out advice is a question he has to answer."

The mayor's task force ultimately decided to recommend a thorough scrubdown, with soap and water, of floors, walls and furniture throughout the building. Since last week, a 71-man crew from the Department of Environmental Services and volunteers from Lorton Reformatory and various halfway houses has been performing this mission.

Thirty members of the work crew were treated for gas-related ailments last Wednesday, while employes continued to work half-shifts or, in some cases, to stay away altogether.

A number of key offices, all located away from the police weapons and ammunition storage room where the explosion occurred, were fully re-opened on Thursday, Switchboard operators and tax officials, among others, returned to eight-hour shifts.

Although the building is set to resume full operations today, its main entrance, on Indiana Avenue between 3d and 5th Street NW, will be closed indefinitely. Visitors should use the C Street entrance, a police spokesman requested.