Nine fires in the last week in an elegant turn-of-the-century apartment building in Kalorama have put city fire and police investigators on the trail of an arson suspect they think lives in the building.

Tenants in the 42-unit building at 2230 California St. NW, have told investigators the fires, all minor, may have been set by a resident angered at the owner's recent decision to sell the building and allow its medium price rental units to be converted to luxury condominiums with price tags of $100,000 and up.

The building called the St. Nicholas, is scheduled to be sold Monday. Only two of the 34 remaining tenants in the building have indicated an interest in buying a condomimium there, and the others face eviction, several residents said.

Seven of the nine fires were set within minutes of each other late Saturday night and early Sunday morning. They followed two other fires earlier last week, one of which caused some residents to flee the building temporarily.

"I know these are little fires," said one resident who, like many of the building's other tenants, asked not to be identified. "But what if we don't catch one (fire) before it gets big? What if he starts a big one? My little girl couldn't sleep, so I sent her to stay with my grandmother."

The building is a brown brick structure with two wings and spacious marble common rooms.

Many of the tenants are elderly women. The Spanish Embassy has an office in the building.

Valuable antiques, paintings and rare rugs fill several of the apartments belonging to the widows of generals, diplomats and politicians who once tenanted the St. Nicholas. In recent years, some younger tenants have begun moving into the building as the widows died or moved away.

After the last fire Sunday, residents of the building hired a private security guard and attack dog to stand at the building's entrance.

Residents also have cleared the common rooms and basement of furniture; sealed three of the four entrances to the basement and done away with a more than 25-year-old practice of putting their trash outside their doors for the janitor to collect.

Four of the fires were set in trash bins left outside apartment doors or in the building's stairwell. Two others were set on a bed and a rug in a basement apartment. The arsonist did not break into the apartment but apparently had a key, residents said.

The arsonist also apparently has a key to the front door of the building which is kept locked 24 hours a day.

In addition, master keys to the apartment units have been missing from the front desk, according to the residents.

Frank Flower, owner of the building who lives in Shaker Heights, Ohio, said in a telephone interview yesterday that he is sure the arsonist is someone who knows the building well - either a present or former resident - and has access to the building.

"My feeling is that it is an angry resident who is mad about having to get out in 120 days," he said. "But arson is a terrible thing. It is putting the fear of God in those people."

Virginia Page, a Washington real estate developer who is buying the building from Flower, said she has no idea who is starting the fires. She said the fires will not dissuade her from buying the property.

"I want some money coming out of the building until I start converting it," she said. "the fires don't benefit me."

She said the apartment on top of the building, a four-bedroom unit with a sundeck and a "magnificent view of the city, will be sold for $170,000.

"The people here are scared but (the arson suspect) hasn't done much more than use matches on some newspapers, rugs and mattresses," said John Thompson. "He hasn't done anything big yet."

Thompson said some odd things happened during and after the rash of fires last weekend: the clock at the switchboard was moved ahead three hours, the lampshades in the halls were set at twisted angles and a policeman's nighstick was stolen after it was left on a table.