CHESAPEAKE, VA. — What started out as an eighth-grade science experiment at a Virginia school became an alarming discovery: Turning down the school air conditioning system during nights and weekends was creating conditions suitable for mold growth in dozens of classrooms.

A group of students at the Great Bridge Middle School caught the attention of school officials recently by establishing a link between HVAC system usage, classroom humidity levels and mold growth. The students recorded temperature and humidity in 30 classrooms throughout the school using data loggers, and they used accompanying software to generate timestamped graphs that compared humidity levels during and after normal school hours.

"About half the square footage of our school is newly remodeled, and moisture doesn't seem to escape as well as it does in the old building," said science teacher Stephen Sawyer, who led the project. " There was visible mold growth on some of the classroom walls. So, while the students were tracking temperature and humidity levels, they took mold culture samples from the rooms and kept track of growth rates in petri dishes."

The students learned that the changes in the humidity from day to night, and from school days to weekends, were dramatic, he said. The readings fluctuated from the low 30% range ends, and within a few weeks some of the mold samples had grown to 90% coverage of the petri dishes.

The experiment, conducted as part of a K-12 energy contest was originally designed to look at the efficiency of the school's HVAC equipment using HOBO data logger kits lent to the yer said. The idea to investigate the HVAC system connection to mold growth came in the wake of staff complaints about breathing difficulties.

"A few of our older staff members, who never had any breathing problems in the old building, all of a sudden were having issues in the new building,"