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Does ice increase the humidity of its surroundings? I'm trying to use the BME280 for an Arduino project regarding locating ice, but I don't know whether the atmosphere is more humid around ice. I'm trying to see whether humidity increases near ice.

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    $\begingroup$ It can do both very much depending on the air around your machine $\endgroup$
    – Alchimista
    Jan 19 '20 at 7:28
  • $\begingroup$ What is a BME280 ? It might help your answer if you were able to tell us what it is. One option for humidity sensing at low temperatures would be a quartz micro-balance combined with a peilter cooler. $\endgroup$ Jan 20 '20 at 18:43
  • $\begingroup$ Why not sensing for T? One should really know the setup and the scenario in which it will operate. $\endgroup$
    – Alchimista
    Jan 23 '20 at 10:59
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It depends on the current humidity.

Water vapor certainly does evaporate from ice, as you can see in a vapor pressure chart. If the humidity is 100%, and the air temperature is the same as that of the ice, then the evaporation and condensation are in equilibrium; i.e. water evaporates as fast as it condenses, so there is no net change in humidity.

However, if the ice is warmer than the air, or the air has less than 100% moisture content at that temperature, then ice will evaporate more than it condenses, raising the humidity.

Conversely, if the ice is colder than the atmosphere, it can lower the humidity.

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No. It is the contrary. Water from the atmospheric humidity is condensed on objects whose temperature is 0°C.

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    $\begingroup$ In order for condensation to occur, local relative humidity must reach 100%, so actually, yes, the ice does increase the relative humidity of its immediate surroundings by cooling the air. . . $\endgroup$
    – Andrew
    Jan 18 '20 at 20:39
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    $\begingroup$ Not to mention that if the air initially has no humidity, then the ice will humidify the air. $\endgroup$
    – MaxW
    Jan 18 '20 at 20:41
  • $\begingroup$ Atmospheric humidity condenses on surfaces with temperature below its dew point. it may be above or below 0 °C. Stratospheric humidity would not condense even on surface with temperature -50 °C, if its dew point is -80 °C ( what is common ). $\endgroup$
    – Poutnik
    Jan 19 '20 at 7:32

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