Fire Chief Roger Audette said the quick response from city firefighters — and an operational sprinkler and alarm system — subdued a potentially dangerous fire downtown on Monday.

The fire at 227 Water St. was reported by an alarm around 4:40 p.m. Monday. Firefighters closed down a portion of Water Street until about 5:45 p.m.

There was heavy smoke on the third floor, Audette said, but it was not visible from the street.

He said the fire started in a third-floor apartment’s closet after rags, coated with a combination of wood stain and polyurethane used to finish hardwood flooring, “spontaneously combusted” because they were not disposed of properly.

Audette said the fire was not suspicious.

“It was in a bad spot,” he said. “It could have gone up into the attic, (where it would have been more difficult to fight).”

Audette said a sprinkler head in the closet kept the fire down until crews could extinguish it completely. He said there was “quite a bit of damage” to the building, as well as water damage to some electrical systems.

No one was hurt in the fire.

The building, which contains Guerrette Properties and other businesses, is owned by Smithtown Four LLC, according to city tax records. Representatives from Guerrette Properties did not return a request for comment by presstime.

Crews from Gardiner, Chelsea and Hallowell offered station coverage while Augusta crews were on the scene.

Code Enforcement Officer Keegan Ballard said the city uses the National Fire Protection Agency Life Safety Code, as recommended by the state fire marshal’s office. He said the code does not require sprinklers in buildings explicitly. Ballard said fire protection standards for buildings are done on a case-by-case basis.

“New mixed-use occupancies are required to have a sprinkler or fire separation,” he said. “It really depends on the use (of the building) or if the floors above are utilized.”

Ballard said the city relies on separation between residential buildings to mitigate the risk of large fires engulfing multiple structures. In a downtown area where buildings are connected, he said, fire safety protocols are much more important.

“It’s absolutely very important,” Ballard said of using the standards. “In a downtown where there’s no separation, it’s crucial … to buying time for emergency services to get there.”