Dew point

Dew point (Td)

The dew point describes the temperature point at which the relative humidity is 100% and the existing water vapour in the air would immediately begin to condense into water.

Can be measured with:

✓ Measurable with air-Q light, air-Q basic and air-Q pro as well as air-Q science


The dew point (Td - d stands for dew point) is the temperature below which water vapour in the air condenses into water. At this temperature point, the air is completely saturated with water, i.e. the relative humidity is 100%, so that the air has reached its maximum capacity for water absorption.

The warmer the air, the more water vapour it can absorb. This means for the dew point: the more water vapour there is in the air, the higher the dew point. Dew point and relative humidity are therefore directly related and can be calculated in each case.

There are two different ways to determine the dew point. In the direct method, the measurement is carried out with the help of a so-called dew point mirror hygrometer, which determines the dew point on the basis of the changing optical characteristics and the reflection behaviour of the mirror.

With the indirect method, on the other hand, the absolute humidity is determined by means of the temperature of the room and the relative humidity. This makes it possible to calculate the temperature at which the humidity will reach 100% saturation.

Limit values for the dew point:

There are no official limit values for the dew point. Recommendations for relative humidity also directly result in dew points. At room temperature, the recommended lower limit of the dew point is approx. 9°C - below this, the air would be perceived as too dry. The upper limit of the dew point is approx. 15°C - above this the air would be perceived as too humid.

Designationning Limit values dew point
General recommendation Minimum value 9 °C
General recommendation Maximum value 15 °C

Consequences of a dew point that is too high or too low:

Temperatures can vary within a room. This poses a problem if, for example, the dew point is undershot on cooler exterior walls. Water can then condense and mould can develop.

Emergence of the dew point:


Sensor used:

The dew point is calculated in the air-Q on the basis of the Magnus formula (currently still without including the air pressure). The values required for this are measured with high accuracy via the temperature sensor as well as sensor for the relative humidity.

Measure dew point:

The air-Q air analyzer can also measure the dew point and other indoor air parameters in real time with one of its sensors, in addition to absolute and relative humidity. You can order the air quality meter in the online store.

air-Qs, which use the sensor for

Dew point (Td)


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