Fumes from a carburetor cleaning fluid were spread through the Gaithersburg High School ventilation system yesterday morning, sending 22 students and staff members to local hospitals to be treated for nausea, dizziness and, in one case, acid burns.

The school was closed after the fumes were discovered.

School officials said all of those taken to Montgomery General and Shady Grove Adventist hospitals were treated and released.

Gaithersburg Principal Dr. Frank J. Masci said the fumes came from a solution that a student used Thursday night to remove graffiti he had painted on a wall last week.

Masci said the student was caught vandalizing the school March 19, but, school officials did not press charges against the youth on "the condition that he clean the wall."

He said the student had been unsuccessful earlier this week in removing the stains "with materials authorized by the school -- we said no chemicals should be used -- so, he apparently came back Thursday night around 11:30 and tried the carburetor fluid. We had insisted that the scrubbing be authorized. But this of course was not."

Masci said the fumes were noticed near the wall by some of the building services staff who arrived at the school at 7:30 a.m. But, Masci said, "The problem really began when the heat was turned on."

Montgomery County police spokesman Sgt. Richard Williams said outside air vents carried the fumes inside the building through the ventilation system. He said police visited the boy's home yesterday and said the boy was not adversely affected by the fumes. Williams said the youth will not be charged in the incident.

Montgomery County schools spokesman Bill Henry said the classes will resume Monday, and disciplinary action against the student is pending.