What factor determines how much moisture is present in a room?

Relative humidity (RH) is the key factor that determines how much moisture is present in a room because it measures the amount of water vapor in the air compared to the maximum amount of water vapor that the air can hold at a specific temperature. When the relative humidity is high, it indicates that the air is near saturation with moisture, which can lead to condensation and potentially create an environment conducive to mold growth.

While temperature influences the capacity of the air to hold moisture—warmer air can hold more moisture than cooler air—it is the relative humidity that directly reflects the moisture content present in the environment. Air pressure can affect weather patterns and can play a role in certain conditions, but it does not directly indicate moisture levels in a room.

Ventilation affects moisture levels by allowing moist air to escape and drier air to enter, which can help regulate humidity. However, it is still the relative humidity that serves as the direct measure of moisture currently in the air regardless of the influences of ventilation and other factors. Thus, understanding relative humidity is essential for assessing moisture levels effectively and preventing issues like mold growth.