Humidity control in a conditioned space is done by controlling the amount of water vapor present in the air in the space. When relative humidity at the desired temperature set-point is too high, dehumidification is required to reduce the amount of water vapor in the air for humidity control. Similarly, when relative humidity at the desired temperature set point is too low, humidification is required to increase the amount of water vapor in the air for humidity control.

Commonly used dehumidification methods include:

1. Surface dehumidification on cooling coils simultaneous with sensible cooling.

2. Direct dehumidification with desiccant-based dehumidifiers

Humidification is not always required in an HVAC system but, when required, it is provided by a humidifier. Commonly used humidification methods include:

1. Water spray humidifier

2. Steam pan humidifier