Lexington, MA- By Bethan L. Jones, Lexington Minuteman

The fire department evacuated the science building at Lexington High School due to high carbon monoxide readings more than once last week.

After several incidents, a hole in the intake pipe and an unlined chimney proved to be the problem.

The fire department was called to LHS a week and a half ago for readings in the science building boiler room over 10 parts per million, a level considered the threshold for carbon monoxide gas. The building was evacuated and ventilated and the readings returned to normal.

Last Thursday at around 5 a.m. the fire department was again called to the science building because of an odor in the building. Fire teams found 25 ppm of carbon monoxide in the building and more than 65 ppm approaching the boiler room. The building was again evacuated, the boilers shut down and the entire facility ventilated, said Lexington Fire Chief William Middlemiss.

The readings were back to normal by 6 a.m. and the building was opened again.

It was on Thursday, as Ham and some consulting engineers examined the boiler system to find a cause for the problem, that the unlined chimney was discovered. Ham said there was also concern the intake and exhaust pipes were placed too close together. Suggestions were made, but at around 11 that night, the carbon monoxide detectors registered large amounts of the gas. The building was then closed by the fire department until a solution could be found.

“After Thursday … the school was not allowed to reoccupy until cleared,” said Middlemiss.

Ham said the absence of a liner comes down to a simple oversight; when the school was renovated, a liner was not included in the specs for the project.

According to Ham, the exhaust does not move through the chimney as effectively, causing dampness which decays the mortar without a chimney liner.

Ham said precautions have been taken, including the installation of 23 carbon monoxide monitors in the high school and all readings are now normal. The LHS science building has been open since Monday.

Middlemiss said the school department is continuing to monitor the situation but all readings as of now are zero ppm.