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DESIVENT
WHAT IS HUMIDITY?
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There is always in everyday life moisture in the air around us.
When scientists measure this moisture they call it humidity. To
get some idea of how much moisture or humidity is in the air, think
of an object with a volume of 1m3. On a hot day, the air inside
such a volume could hold around 15g of water vapour H2O.
However, as its in gaseous form, its invisible.
What's interesting about humidity, is that on a cold
day the same area may only hold 5g of H2O.
The secret of understanding humidity is that hot
air can hold more moisture than cold air. Scientists have used the
term Absolute Humidity to indicate the number of grams of water
vapour in a cubic meter of air.
However, the most commonly used term for humidity
is Relative Humidity. This takes into account the fact that hot
air can hold more moisture than cold air. It also takes into account
that the level of moisture in the air is influenced by the availability
of moisture to the air. Thus, for a particular temperature, if the
air contains 60% of the moisture it can hold at that temperature,
the relative humidity will be designated at 60% Relative Humidity
(60%RH)
Relative Humidity is commonly used because it corresponds with our
own sensations of moisture. On a cold damp day, the relative humidity
may be 90%RH. On a hot dry day the RH% may be 50%.
So to summarise, humidity is a measure of
how much moisture is in the air.
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ABOUT MOISTURE