Dew point (Td)
air-Q with a dew point sensor
Description:
The dew point (Td – d) is the temperature below which water vapor in the air condenses into water. At this temperature, the air is completely saturated with water—that is, the relative humidity reaches 100 percent—meaning the air has reached its maximum capacity to hold water.
The warmer the air, the more water vapor it can hold. This means that, with regard to the dew point: the more water vapor there is in the air, the higher the dew point. The dew point and the relative humidity of the air are therefore directly related and can be calculated based on each other.
There are two different ways to determine the dew point. In the direct method, the measurement is taken using a device called a dew-point mirror hygrometer, which determines the dew point based on changes in the mirror's optical properties and reflective behavior.
In the indirect method, however, the absolute humidity of the air is determined based on the room temperature and the relative humidity. From this, it is possible to calculate the temperature at which the air’s humidity will reach 100% saturation.
Dew point limit values:
There are no official limit values for the dew point. However, dew points can be directly derived from the recommendations for relative humidity. At room temperature, the recommended lower limit for the dew point is approximately 9°C—below that value, the air would be perceived as too dry. The upper limit for the dew point is around 15°C—above this value, the air would be perceived as too muggy.
| Denomination | Dew Point Limit Values |
| 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 when, for example, the temperature on colder exterior walls drops below the dew point. Water can then condense, and mold may form.
Origin of the dew point:
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Sensor used:
The dew point is calculated in the air-Q based on the Magnus formula (currently without taking atmospheric pressure into account). The values required for this calculation are measured with high precision using the temperature sensor and the relative humidity sensor.
Measuring the dew point:
The air-Q air analyzer can use one of its sensors to measure not only the absolute and relative humidity of the air, but also the dew point and other indoor air parameters in real time. You can order the air quality monitor from the online store.
More measured values / sensors
