School officials are taking steps to ventilate Newfound Memorial Middle School after unusually high levels of carbon dioxide were detected.
Inspectors testing energy efficiency at the school made the discovery and determined that the source of the carbon dioxide is the students themselves.
"As you know, as students exhale, they produce carbon dioxide and they release it into the atmosphere," said Superintendent Marie Ross.
But the aging ventilation system can't pump out all the carbon dioxide that students are exhaling. The district said a harmless but elevated amount of the gas lingers in the classrooms.
"As I said, I don't have a serious concern about the health hazards," Ross said.
Because students can't hold their breath for the whole school day, the school opens its windows at lunchtime. Officials said they will also let parents know about the problem.
"I'm sure that if it was at a level that was high enough to cause concern, then they would close the school," said Susan Colby, of Bristol.
The district said it is hoping the town will approve a plan to improve the ventilation system. The plan is expected to be presented this spring.