Mold is a type of fungus that can grow indoors and outdoors, and thrives in moist, warm environments. When mold spores land on a wet or damp surface, they begin to grow and reproduce.
Mold can cause a variety of health problems, including respiratory illnesses, allergic reactions, and skin and eye irritation. People with asthma, allergies, or weakened immune systems are especially susceptible to the health effects of mold.
Mold growth in homes and other buildings is often the result of water leaks or flooding. However, mold can also grow in buildings with poor ventilation and high humidity levels. Heating, ventilating, and air conditioning (HVAC) systems can play a role in mold growth, as they can circulate mold spores throughout a building.
To prevent mold growth, it is important to keep indoor humidity levels low and to quickly fix any water leaks or flooding. Regularly cleaning and maintaining HVAC systems can also help to prevent mold growth.
https://www.cdc.gov/mold/dampness_facts.htm
https://www.mayoclinic.org/diseases-conditions/molds/symptoms-causes/syc-20371787
https://www.epa.gov/mold/molds-and-your-home