Hilles Library was evacuated yesterday morning after gasoline fumes entered the building's heating and ventilation systems.

Library staff and students said they smelled what seemed to be gas on the first and lower main floors of the library, said Suzanne G. Temple, associate librarian at Hilles.

Temple evacuated the staff and about 20 students at approximately 9:15 a.m. The Cambridge Fire Department's gas response team arrived minutes later and checked the entire building for signs of natural or noxious gas but detected no harmful gases, Chief Deputy John J. O'Donoghue said.

The gasoline had apparently been spilled near a shed that stores snow blowers, about 50 feet from an air intake valve outside the library, according to O'Donoghue. He said vaporized gasoline entered the building through the valve and spread through the library's heating and ventilation systems.

"It was not a hazard, just a smell of gasoline from outside," said O'Donoghue.

'Negligible Traces'

He said the team found only "negligible traces" of combustible gases in the library during its half-hour search.

Temple said no one reported smelling gas later in the day. "The smell has dissipated and we haven't smelled any fumes," she said.

The fire department does not plan any further investigation of the matter. "This case is done," O'Donoghue said.