Condensation occurs where air meets a surface that is below the dewpoint temperature. This is mainly in winter or in warmer weather on cooling coils when mechanical cooling is needed.

Humidification is mainly used in hospitals and when the outdoor air contains very little moisture. (Winter or Desert). Hospitals have high ventilation rates, sick people and immune compromised people. Without humidification, the humidity in the occupied space can drop far below the optimum for health and comfort of around 50%