Humidity in Pharmaceutical Area:Absolute Humidity vs. Relative Humidity

Air humidity is a very important parameter during drug  R&D, production and storage.   When we talk about humidity, two definitions are easy to confuse,  absolute humidity and relative humidity. What are the relationship and difference between this two measurement of humidity?

Absolute humidity is a measure of water vapor (moisture) in the air, which means the mass of water vapor per unit volume of gas (grams of moisture per cubic meter of air) .  Absolute Humidity international uints is (g/m3).In pharmaceutical area, absolute humidity is not used too much, as it is difficult to measure the value.  And relative humidity is more common to use during production and storage of pharmaceutical products.

Relative humidity is a measure of water vapor (moisture) in the air at a certain temperature compared to what the air can hold at that temperature.

It is a important index in pharmaceutical area. Humidity in the warehouse should be 45%～75% in the medicine warehouse. And the relative humidity need to be controlled well while doing stability research, and during production.

Relative humidity is the percentage of absolute humidity to saturated humidity. The relative humidity of the air in a certain environment can be measured by a hygrometer. At present, there are both dry and wet bulb hygrometers and electronic hygrometers in production.

Saturated humidity is related to the temperature, so the value of relative humidity is related to the temperature.

The conversion formula for absolute humidity and relative humidity is n=(PV)/RT, m=18n=(18PV)/(RT), where n is absolute humidity and m is relative humidity.

 Relative Humidity and Dew Point are both measures of moisture in the air.The dew point is the temperature to which air must be cooled to become saturated with water vapor. Dew point is related to Relative Humidity. The higher the Dew Point temperature, the greater the moisture content of the air.