Marshalltown High School will have virtual classes Friday.

The decision was made in response to concerns of odd smells and visible fumes on Tuesday. Building ventilation will occur Friday, and additional testing will be conducted to confirm previous results.

The smells were detected in the area of the Career and Technical Education wing construction project, which had ongoing welding and demolition work being done.

Marshalltown Fire Department Marshal Josh Warnell was called to the scene and conducted four-gas monitoring. No elevated levels of any dangerous gasses were ultimately detected.

Warnell said there is not a way to estimate how quickly the gas can air out of an area. It depends on how much gas was present, and the ventilation in place. Warnell saw open windows and multiple fans.

“There were acceptable levels of ventilation by the time I walked through,” he said.

The construction crew, as part of standard operating procedure, had several air quality monitors placed in the construction area which were fully functional and giving acceptable readings.

In a Thursday press release, Marshalltown Community School District leaders shared that upon hearing concerns, construction work ceased, and crew members set up additional monitors to register acceptable air quality readings. The construction crew has limited use of certain equipment and will perform odor-producing work after school and on the weekend when students and staff are not present.

Multiple individuals notified the T-R on Thursday and reported that teachers in classrooms close to the construction area were absent as a result of feeling ill. The press release confirmed a few MHS staff members and students did report symptoms as a result of the odors to the school nurse and local physicians.

Warnell could not confirm the illnesses, but said carbon monoxide (CO) can cause people to feel sick — how sick, he added, depends on the levels of the gas. Lower levels of CO can create flu-like symptoms — headaches, fatigue, nausea, chest pain, dizziness and disorientation. Higher levels can create impaired vision in addition to the flu-like symptoms.

“Depending on the level, (being) subject to carbon monoxide has a large factor on the health implications,” Warnell said. “Lower levels over a long period of time can produce symptoms.”

He added that CO is odorless.

Symptoms relating to this situation should disappear within 24 to 48 hours, the press release stated. The district also consulted with the Bureau of Student and Family Special Education Services at the Iowa Department of Education, the Iowa Health and Human Services and the Iowa Poison Control Center. Officials have requested the Occupational Safety and Health Administration (OSHA) to review the situation and plans to move forward safely with construction.

The press release stated all entities are satisfied with the district’s response.

Contact Lana Bradstream at 641-753-6611 ext. 210 or lbradstream@timesrepublican.com.