What is the term for the temperature at which air reaches 100% relative humidity?

Dew point temperature is the temperature at which an air mass becomes saturated (100% RH) and can hold no more water vapor. In WRT psychrometry, this is a critical “threshold” condition because any additional cooling of the air (at the same moisture content) forces water vapor to change state and condense onto cooler surfaces. The WRT body of knowledge emphasizes that as air is cooled, its capacity to hold water vapor decreases until RH reaches 100%, which is the dew point condition.

In water damage restoration, dew point is used operationally to manage secondary damage risk and to confirm drying potential. The WRT reference explains that restorers compare the dew point of the indoor air (often the most humid air mass in the structure) to material surface temperatures throughout the affected environment. If a surface temperature is below the dew point, condensation will occur on that surface, potentially increasing moisture loading and causing secondary damage. Conversely, when surface temperatures are warmer than the dew point of the surrounding air, evaporation potential increases, supporting restorative drying.

Because dew point is directly related to humidity ratio and vapor pressure, it also functions as a practical indicator of “how wet the air really is” regardless of temperature changes. This is why dew point is repeatedly referenced alongside vapor pressure and humidity ratio as a foundational psychrometric measurement used to evaluate drying systems and to prevent condensation events during mitigation.

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