As students and staff return to school, anticipation for the year ahead is palpable. However, one unwelcome surprise that everyone hopes to avoid in their classrooms is the presence of mold.

During summer break, the combination of reduced ventilation to conserve energy and increased cleaning and construction projects can contribute to elevated indoor humidity levels, which creates the perfect conditions for mold to thrive in schools. Understanding the factors that contribute to mold growth in schools and engaging staff in the preventative maintenance and early reporting of moisture problems can be effective strategies in school mold prevention programs.

Understanding suitable conditions for mold growth

The Environmental Protection Agency (EPA) recommends keeping indoor relative humidity between 30 and 50% to prevent mold growth, which presents a unique challenge in regions with high relative humidity in the outdoor environment. When warm, moist air enters a building envelope, water vapor may form condensation on building materials. Saturated wallboard, insulation or ceiling tiles can serve as a food source for mold spores and a catalyst for fungal growth in the indoor environment.

Exposure to mold may cause respiratory or allergic symptoms, especially for building occupants with existing health conditions. Mold is able to grow wherever there is moisture and an organic substrate, like wood or drywall. Therefore, the key to prevent or minimize indoor mold growth is to actively maintain, inspect and correct buildings for moisture problems.

Key components of effective school mold prevention programs

Staff training: School staff should have clear instructions on what mold growth can look like and how, when and to whom they should report mold or moisture concerns.
Efficient feedback loops: Reported concerns should be directed to the appropriate specialists to investigate and, if necessary, remediate moisture problems in a timely manner.
Transparent communications: After investigating reported concerns from school staff, specialists should communicate their findings and any appropriate response actions whether visible mold is observed or not.
Regular building inspections: In a high-moisture indoor environment, mold can start to grow within 24–48 hours. Routine building walkthroughs can help identify sources of water damage before fungal growth occur.

Photo credit: Orange County Public Schools.

Case Study: Orange County Public Schools, Florida

Few regions of the U.S. are more accustomed to high humidity than the Sunshine State.

Located in the subtropical climate of Central Florida, Orange County Public Schools (OCPS) is the eighth largest school district in the country and the fourth largest in Florida with over 200,000 students and 25,000 staff members. Within the district’s 210 school facilities, one of the main indoor environmental quality (IEQ) concerns is mold growth.

During the summer months, average relative humidity is 58–91% in Orlando, Florida, which is Orange County’s largest city. This presents a unique challenge for OCPS, as the risk for mold growth is high but the capacity for monitoring and reporting IEQ concerns is limited by the lack of building occupants due to summer break. According to the senior director of the environmental compliance and sustainability division (ECSD), Jennifer Fowler, the department has historically been inundated with reports of mold growth after students and staff return for the start of school.

In order to combat the influx of IEQ complaints and necessary remediation efforts, ECSD implemented a summer inspection program in 2015. School administrative staff are required to complete weekly walkthroughs of their facility throughout the summer vacation period in order to identify odors, signs of mold growth or moisture problems. After completing the walkthrough, the administrative staff member is responsible for entering the data into the ECSD’s IEQ tracking spreadsheet and submitting work orders, if necessary. After receiving the work orders, ECSD is responsible for investigating the complaint within three days.

Orange County’s summer inspection program reduced the number of reported IEQ concerns overall and resulted in a 100% reduction in major IEQ events.

In accordance with EPA guidance, OCPS’s indoor air quality (IAQ) assessment characterization matrix classifies major mold events as greater than 100 contiguous square feet of visible mold, moderate events as between 10 and 100 square feet, and minor events as less than 10 square feet. ECSD developed this matrix based on the hazard and exposure characterization of the relevant IEQ concern. Designating a risk category allows the department to prioritize IEQ events and streamline the appropriate response actions.

Fowler recognizes that ECDS’s standardized operating procedures and collaboration with school staff have been integral to the department’s success. Most importantly, establishing a transparent decision-making process has built trust between the department and school administrators, leadership and maintenance staff. This interdepartmental collaboration at OCPS has helped to build a comprehensive mold prevention program that ensures students and staff return to a healthy learning environment in their classrooms.

Additional resources

Other helpful resources on mold prevention include

Learn more and take action using the School District IAQ Management Plan Toolkit

School mold prevention programs help keep schools healthy