Massachusetts Department of Public Health seal Massachusetts Environmental Public Health Tracking


image show a school hallway with papers on the floor.Moisture is the most common cause of mold growth. Although molds are pervasive in both indoor and outdoor environments, active mold growth and odors indicate that too much moisture is present. Indoor mold growth occurs when spores land on wet materials that can be a food source for mold. Mold growth indoors points to the presence of a water source, which can include leaks from plumbing or roofs, floods, condensation, or entry via the building exterior. Mold and fungal growth may also happen when indoor relative humidity is in more than 70 percent for a few days. When building materials become water-damaged, appropriate actions must be taken to prevent mold exposure

What are Ways to Prevent Mold Growth?

The best way to prevent mold growth is to prevent/control water that is entering and exiting a building. Controlling moisture and preventing mold growth avoids damage to building materials and prevents mold exposures that can lead to allergic reactions, including asthma. Methods for controlling water in a building include:

  • Reducing indoor humidity by using dehumidifiers or dedicated exhaust ventilation in bathrooms/shower areas and cooking areas
  • Insulating and ventilating the building to prevent condensation
  • Periodically checking the building for signs of water or mold growth
  • Responding promptly to reports of leaks
Did You Know?

The key to mold control is moisture control.

When water damage is discovered, it is important to examine the materials that are wet. Some materials, such as hard plastics, brick, and metals, do not support mold growth. These materials can be cleaned with water and a detergent. Absorbent, carbon-containing materials such as ceiling tiles, manufactured wood and gypsum wallboard materials, and carpets can serve as a source of food for molds. These materials should be removed and replaced if not dried between 24 to 48 hours after becoming water-damaged. The Massachusetts Department of Public Health (MDPH) has developed guidance for preventing and identifying water damage in schools and public buildings.

What About Indoor Air Quality and Moisture in Public Buildings?

During an assessment, Indoor Air Quality Program staff examine both the interior and exterior of a building for sources of water and identify any signs of water damage. Staff may also take moisture measurements; however, mold testing is not conducted or recommended in any building types since there are no standards or limits for comparison. Commonly observed signs of water damage in schools and large buildings include stained ceiling tiles, damage to cabinets and countertops in sink areas, and spills on carpets.

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