Humidity

In order to understand relative humidity, let’s look at what humidity is all about. The term humidity is mainly used for the moisture that is present in the atmosphere. Understanding humidity in terms of geography, water in the rivers, lakes, oceans and other water bodies is absorbed by solar radiations when heat is generated by a process called evaporation. This process results in large amounts of water evaporating into water vapor present in the atmosphere. Water vapor condenses in the form of rain, snow and clouds by a process called condensation. You can read more about condensation in our previous article, “What is Condensation?”

Relative Humidity

Researchers have tried to find out different ways to measure humidity in order to analyze significant factors like climatic conditions in different regions. Among the different ways of calculating humidity, relative humidity is the most commonly used method. Relative humidity is basically the amount of water vapor or moisture that is present in the atmosphere. It is the amount of water vapor present in the air at any given time relative to the amount that is required to saturate the atmosphere,

i.e., Relative Humidity = actual vapor density/saturation vapor density × 100%

If the presence of water vapor goes beyond saturation, it condenses as dew. Relative humidity increases when the unsaturated air is cooled. When the air reaches saturation point, relative humidity is 100%.

Considerations When Measuring Humidity

Have you ever thought why it is essential to check the level of humidity? There are basically two reasons, maintenance of hygiene and energy efficiency. Lack of control in humidity leads to mold formation, corrosion and persistent condensation on cold surface. The ideal and maximum level of humidity is between 30 and 40%.

Humidity occurs as a result of fluctuations in temperature. For this reason, it is necessary to consider temperature while measuring relative humidity. As mentioned earlier, temperature is responsible for saturation vapor pressure. High and low levels of humidity have a significant effect on relative humidity, as well as saturation pressure. Therefore, the exact temperature makes the comparison in humidity measurement values easier.

Another factor to take into consideration when measuring relative humidity is the location and stabilization. Short distances can also have variations in relative humidity and it is always wise to have patience till the conditions are stabilized, including temperature.

How Do We Measure Humidity?

There are a number of devices that can be used to measure humidity. Relative humidity can be measured by the following instruments:

1. Sling Psychrometer: It consists of two thermometers, a wet-bulb and a dry-bulb thermometer. The thermometers function on the basis of the evaporation and cooling that takes place in the atmosphere. When evaporation occurs, the temperatures in both the thermometers show different values and their differences are noted down (wet-bulb depression) to calculate relative humidity. On the other hand, these thermometers would have the same temperatures if there was no evaporation.

2. Hair Hygrometer: This device is based on the calculation of the differences in the length of strands of hair during humidity. As the hair becomes longer, the humidity also increases.

Importance of Relative Humidity

1. Climate

Relative humidity does play a vital role in climatic conditions, especially when there is a fluctuation in temperature which decides human comfort, health and safety, and technical requirements of machinery and processes.

2. Comfort

Human beings tend to be quite uncomfortable during seasons when the relative humidity is very high. Humid conditions make people perspire to a lesser extent than dry weather conditions. Hence, we feel much warmer during high levels of humidity than lower levels of humidity.

3. Buildings

In order to maintain the temperature in the surroundings, there should be a control in relative humidity. High temperature and low humidity leads to rapid evaporation of water that result in dry soil, quick drying of clothes, dry sweat and shrinkage of wooden furniture that could damage the paint. However, high temperature and high humidity leads to slow evaporation of water which leads to growth of mold and mildew, corrosion, decay and other damp-related issues. Similarly, relative humidity needs to be controlled in buildings such as factories, hospitals, laboratories and other facilities using devices such as humidifiers and dehumidifiers to avoid such issues.

4. Vehicles

You must be wondering as to how vehicles would get affected by humidity. High humidity inside the vehicle can lead to condensation on the windows while driving and electrical problems. Airliners, submersibles and spacecrafts are also prone to condensation, corrosion and health problems such as drying out of mucosa, dry skin and sore eyes.

For more on basement related solutions, click on to www.keystonebasementsystems.com.

“Keystone Basement Systems, Inc. is a foundation repair company. KBS is not, however, an engineering firm and should not be considered as such.”

References

1. http://www.ace.mmu.ac.uk/eae/weather/older/Humidity.html
2. http://www.physicalgeography.net/fundamentals/8c.html
3. http://www.sensirion.com/images/getFile?id=115
4. http://www.aemc.com/techinfo/appnotes/environmentaltesters/APP-EnvironTesters-Humidity.pdf
5. http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/relhum.htm

Tags: Article, Basic information, Description, Informative, Overview

This entry was posted on Monday, June 28th, 2010 at 1:55 am and is filed under Basic Information, Certified Professionals, Remedial measures. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.