There is no practical way to eliminate all mold and mold spores in the indoor environment; the way to control indoor mold growth is to control _______.

• A. Humidity
• B. Moisture
• C. Temperature
• D. Ventilation

Answer: (B)

Moisture is the key factor that drives indoor mold growth. Fungi need water to grow and reproduce, so removing or greatly reducing any source of moisture stops mold from flourishing. This means focusing on preventing and eliminating damp conditions: fix leaks and plumbing issues, repair roof or wall leaks, improve drainage around the building, reduce condensation through insulation and ventilation, promptly dry any spills or wet areas, and use dehumidification in consistently damp spaces.

Temperature and ventilation influence how quickly mold grows and how moisture moves, but they don’t remove the essential resource—water in or on materials. Humidity levels in the air matter, yet damp surfaces or damp building materials can sustain growth even when air humidity isn’t extreme. By targeting moisture control—keeping surfaces dry and eliminating prolonged dampness—you limit mold development more effectively than by addressing air humidity or temperature alone.