East Park Elementary School in Fairmont has been facing carbon monoxide problems since early last week.
Superintendent Gary Price said students were evacuated again Thursday after a carbon monoxide alarm went off.
The alarm went off as a test but students were already dismissed for the day.
The Fairmont Fire Department checked the school out and found nothing.
The school board is spending more than $40,000 to fix the problem.
Price said the furnace has been fixed, but a chimney liner needs to be installed.