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Difference between Humidity and Relative Humidity

If talk about the difference between Humidity and Relative humidity both are the same in terms of the presence of water in form of vapors in the air.

Humidity differs from relative humidity in that humidity refers to the presence of water vapor in the air, whereas relative humidity refers to the proportion of water vapor available in a particular volume of air.

In Pharmaceutical RH is an important factor to determine the Quality of products. The RH is maintained through Pharmaceutical HVAC System.

Basic difference between Humidity and Relative Humidity

Humidity: Humidity refers to the amount of H2O vapor in the environment. In general, the evaporation of water from water bodies is caused by sun radiation in the air. This evaporation produces water vapor, which mixes with the air.

Relative Humidity: It is a measurement of water vapor that is relative to the air temperature. It’s calculated as a %age of the total amount of water vapor in the air that might be held at the current temperature.

Warm air can hold more water vapor as compared to cold water

Causes of RH and Humidity

Cold air holds less moisture as compared to hot air. so the Relative Humidity of cold air will be higher than warm air. for eg. at 20°C air can hold up to 10 gm vapor than its RH is 100%, and if we increase the temperature to 21°C then the air holding capacity of water vapor will also increase, and at the same time, RH will decrease.

Relative Humidity Chart

Since warm air can hold more water vapor than cold water. if we lower the temperature then RH will go up.

Useful Thumb Rule to Remember Facts Between Temperature, RH, and Pressure:

The first law is that as the temperature rises, the air becomes drier (RH down), and as the temperature falls, the air becomes wetter (RH Up) (RH increases). When it comes to pressure, the general rule is that as pressure drops, the air becomes drier (RH drops), and as pressure rises, the air becomes wetter (RH rises) (RH Up).

Types of Humidity with explaination

It is of three types: Relative, Absolute, and Specific. here mainly two types humidity is considered

Relative Humidity: It is a measurement of water vapor that is relative to the air temperature. It’s calculated as a %age of the total amount of water vapor in the air that might be held at the current temperature.

Absolute Humidity: Absolute humidity is the actual amount of water vapor or actual mass of water vapor in air volume without consideration of temperature. absolute humidity is expressed in gram per square cubic meter gm/m3.

Comparison Table between Humidity vs Relative Humidity

                 Humidity

               Relative Humidity

Humidity refers to the amount of water vapour in the air

Relative humidity is a measurement of water vapour that is Relative to the air temperature

Temperature to be Considered

Temparature to be Considered

It's Measured in Water Vapour per Cubic meter of air.

It is calculated in percentage

More Water Vapour More Sweat, less water vapour a lot cooler

More Water Vapour results in Higher Relative Humidity and the less water vapour results in less relative humidity.

Role in Pharmaceutical and its Importance

It important factor in pharmaceuticals to maintain the quality of products up to the final stage during manufacturing. the reason for monitoring the RH is to control the moisture at the site of products manufacturing. if RH goes up from the required condition, it can harm the products or degrade the potency of products over the time of long periods.

Humidity is also a significant issue for products that are extremely sensitive to moisture, such as drugs. This is because it can change the product’s qualities to the point that it’s no longer useful, which is why medical pills and dry powders are kept in controlled environments with specific humidity and temperature levels.

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