Originally written by Vanessa Pike-Russell-Updated by Stacy Griffith

What is Humidity?

Humidity is a measure of the amount of water vapor in the air. It can be expressed in several ways.

“Specific humidity” is the mass of water vapor per unit mass of combined dry air and water vapor, generally expressed in grams per kilogram. The specific humidity of an air parcel does not change with temperature.

“Absolute humidity” is the density of water vapor, expressed as grams per cubic meter of air.

“Relative humidity”  is the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water at a given temperature.

Relative humidity depends on temperature and the pressure of the system of interest. The same amount of water vapor results in higher relative humidity in cool air than warm air.

Crabitat too humid? Bring the temperature up a few degrees. A useful rule of thumb is that the maximum absolute humidity doubles for every 20 °F or 10 °C increase in temperature. Thus, the relative humidity will drop by a factor of 2 for each 20 °F or 10 °C increase in temperature, assuming conservation of absolute moisture.

Related terms:

“Saturation,” which describes the condition where water vapor is at a maximum concentration for the air temperature (warm air can hold more moisture than cold);

“Dew point temperature” the temperature at which saturation occurs if air is cooled at constant pressure without addition or removal of water vapor; and

“Vapor pressure,” which in meteorology is that part of the total atmospheric pressure due to water vapor content. Water vapor is a lighter gas than other gaseous components of air at the same temperature, so humid air will tend to rise by natural convection. This is a mechanism behind thunderstorms and other weather phenomena. Beware excess humidity building up in your topper and causing so much condensation that your tank floods.

Relative humidity is normally expressed as a percentage; a higher percentage means that the air–water mixture is more humid. At 100% relative humidity, the air is saturated and is at its dew point. At this point you are are risking a flood in your crabitat. When relative humidity approaches 100 %, condensation can occur on surfaces, leading to problems with mold, corrosion, decay, and other moisture-related deterioration. Condensation can pose a safety risk as it can promote the growth of mold and wood rot.

Reference: Arctic Climatography and Meteorology

Reference: Wikipedia

What is the Ideal Humidity Range for Hermit Crabs?

Humidity should be between 50-60% for Actual Humidity and between 70-80% Relative Humidity(rh).

How can I measure humidity within my Crabitat?

You will need to buy a humidity gauge, also known as a hygrometer.

Calibrate before use.

There are many kinds, some of the more popular are shown below.
[amazon_link asins=’B01HDW58GS,B0013BKDO8,B004K8RF10′ template=’ProductCarousel’ store=’thecrabjour-20′ marketplace=’US’ link_id=’43111d70-f94e-4a8d-a54f-f54e6629ece1′]