Trion Air T707u - Atomizing Humidifier, 6 GPD

 

Relative humidity is a measure of the amount of water in the air compared with the amount of water the air can hold at the temperature it happens to be when you measure it.

Air temperature (Celsius) / Water vapor air can hold at that temp (Saturation vapor pressure)
30°C (86°F) / 30 grams per cubic meter of air
20°C (68°F) / 17 grams per cubic meter of air
10°C (50°F) / 9 grams per cubic meter of air

Based on the above "table," here's how relative humidity works: Imagine that you measure the air's temperature at 30° Celsius (86°F) and you measure its humidity at 9 grams per cubic meter of air. You would divide 9 by 30 and multiply by 100 to get a relative humidity of 30%. In other words, the air actually has 30% of the water vapor it can hold at its current temperature. Cool the air to 20°C (68°F). Now we divide 9, the vapor actually in the air, by 17, the vapor it could hold at its new temperature, and multiply by 100 to get a relative humidity of 52.9% (53% rounded off). Finally, when the air cools to 10°C (50°F), we divide 9 by 9 and multiply by 100 to get a relative humidity of 100%. The air now has all the vapor it can hold at its new temperature.

Once again, the way you measure "relative humidity" is to divide the actual vapor pressure by the saturation vapor pressure and then multiply by 100 to convert to a percent. So, to get the "ideal" 70°/70% conditions in your humidor (give or take a degree or two) you would need a temperature of 68°F and saturation vapor pressure of 11.55 grams per cubic meter of air.

What this amounts to is, the less heat you have the more humidity required, and vice versa to keep the climate balanced.