Nineteen Wootton High School students and a firefighter were treated for toxic gas poisoning yesterday after inhaling hydrogen sulfide fumes apparently released by vandals in the school's offices before classes began for the day.

Montgomery County fire officials said several small vials containing hydrogen sulfide--which smells like rotten eggs--were smashed on the floor in the school's complex of offices. The Rockville school's 1,825 students were evacuated at about 10:30 a.m.

"We think it was some kind of act of vandalism," said Michael Hamilton, fire department spokesman. "By the time we sealed off the principal's office where the vials were found, the fumes had circulated through the ventilation system."

Fifteen students and firefighter Peter Hughes were taken to Shady Grove Adventist Hospital and four other students were taken to Suburban Hospital suffering from nausea, dizziness and stinging eyes.

All who were hospitalized were released. Dr. William Oliphant, the spokesman at Shady Grove Hospital, said those taken to that institution were given chest X-rays, blood tests, oxygen and an eye wash.

The school closed at 12:30 while firefighters ventilated the building and cleaned up. At 3 p.m. the school reopened for afternoon and evening activities, school officials said.