Indoor Air sciences CSMI Practice Exam

When a surface cools down below dew point conditions, what occurs?

1. A draft will form

2. Frost will form

3. Condensation will form

4. A cloud will form

The correct answer is: Condensation will form

When a surface cools down below dew point conditions, condensation occurs. Dew point is the temperature at which air becomes saturated with moisture and can no longer hold all of the water vapor as a gas, leading to the transformation of that vapor into liquid water. When a surface, such as a window or a blade of grass, falls below this temperature, the moisture in the air surrounding it begins to condense into tiny water droplets, forming condensation. This process is influenced by the temperature of the surface; as it cools down, the air in direct contact with it reaches its dew point, resulting in the moisture collecting as liquid. This phenomenon is common in various environments, particularly in humid conditions, where the presence of adequate moisture content in the air facilitates the condensation process. Though frost may form under specific conditions when the temperature is below freezing, and clouds are related to larger climatic conditions rather than surface temperature alone, condensation specifically relates to the air's diminishing capacity to hold water vapor as it cools. Therefore, the occurrence of condensation when surfaces cool below the dew point is a clear and specific outcome of this process.