What occurs when the relative humidity is 100%?

When the relative humidity reaches 100%, it signifies that the air is fully saturated with moisture. This means the air cannot hold any additional moisture in the form of water vapor, leading to the potential for condensation. At this level of saturation, if the temperature drops further or if there is an introduction of additional moisture, water droplets can form, resulting in phenomena such as fog, dew, or precipitation.

The concept of 100% relative humidity is crucial in understanding various weather patterns and conditions, including the formation of clouds and storms, as well as in contexts such as fire alarm systems where humidity can impact both the operation of sensitive equipment and overall safety measures.