Final answer:
To address indoor humidity levels outside the 30-50% recommended range, use a humidifier to increase or an air conditioner/dehumidifier to decrease humidity.
Step-by-step explanation:
When indoor humidity levels exceed or fall below the recommended range of 30 to 50 percent, certain actions should be taken to restore optimal conditions. To increase humidity, one can use a humidifier; while to decrease humidity, options include opening windows, turning on the air conditioner, or using a dehumidifier. These measures are important because relative humidity affects how much water vapor is in the air versus the maximum it can hold, which varies with temperature.
If the relative humidity is, for example, 90.0% at a temperature of 20.0°C, it will decrease when the temperature rises to 30.0°C, provided the amount of water in the air remains constant, due to the increased capacity of warm air to hold moisture. Conversely, if the temperature drops, the relative humidity can reach 100% at the dew point, leading to the formation of dew or fog. Understanding these dynamics is vital to maintaining comfort and preventing issues like mold growth inside buildings.