Humidity: Explanation, Types, and Effects

Ans. Humidity is defined as the concentration of water vapour in the air.

Ans. The relative humidity is defined as the ratio between the vapour contained at a particular temperature and the vapour that could have been contained at that temperature. This ability of air to contain a particular amount of vapour at a particular temperature is the saturation point. We may also define relative humidity as the ratio between partial vapor pressure and saturation vapour pressure of an air-water mixture at a certain temperature. 

Relative humidity is normally expressed as a percentage and can even exceed one hundred percent. If a system has a relative humidity of more than 100 percent then it is called a supersaturated system. 100 percent relative humidity corresponds to the dew point. Researchers and scientists use the concept of relative humidity to predict the weather changes over an area.

On the contrary absolute humidity can be expressed as the total amount of water vapor which is available in a given volume of air. This is expressed as gram per cubic meter or gram per Kilogram of air.

Ans. Electronic devices have the pre-mentioned humidity conditions at which they can be safely operated. If humidity exceeds the limit it may cause short-circuiting or any other malfunctioning in the device. Condensation-related problems are the most common in electronic devices in regions of higher humidity. On the other hand, if the humidity is low, the device components may become dry and brittle. Therefore it is advised that when any electronic device is moved from a low-humidity place to a high-humidity place or vice versa, it must be allowed to get acclimatized for several hours before being used.

Ans. Humidity is a well-known climate-determining factor. In addition to that is the fact that humidity has effects on other climatic parameters as well. The climate of places which are near the equator is highly humid. This condition is due to prevailing winds and overcast conditions. Some places experience high humidity during the rainy season such as Chennai, Kolkata, and Cochin. 

In addition to this vapor is one of the major greenhouse gases. It absorbs the infrared radiation that is emitted by the Earth. Thus humid areas experience more heat than dry areas. This effect of humidity is experienced in desert areas. In the nighttime, humid areas are hotter than dry deserts which cool considerably more at night time. 

Ans. The dew point refers to the saturation temperature at which the air is holding vapor at its full capacity. At the dew point, the air parcel will not accept any more vapor mass into the air-water mixture system. If the temperature is reduced further below the dew point then condensation of vapor starts. The relative humidity in normal cases does not exceed 100 percent, so the dew point in most of the cases is the air temperature. 

At the dew point, the rate of evaporation and condensation becomes equal. Below the dew point, the rate of condensation exceeds the vapor formation rate. The water that condenses at this temperature on any surface in the system is called dew. If the temperature falls below the dew point and still no condensation is observed then in that case the system is said to be supersaturated.

Ans. The construction of an enclosed space like a building, an apartment, a factory, etc requires proper ventilation for the movement of heat with ease. But with growing demand for more building comfort buildings have provisions that resist the external environment making the inside a virtually sealed space. This prevents the movement of heat and moisture through the building. This leads to condensation-related problems in and around the walls of the buildings.

Another problem associated with the construction of buildings is insufficient sealing provisions. This leads to capillary effects of water movement through walls. Two big challenges that need redressal in big complexes is the maintenance of relative humidity neither too low nor too high. For this humidifiers and dehumidifiers are used together with other control systems like HVAC.

Ans. Absolute humidity can be expressed as the total amount of water vapor that is available in a given volume of air. This is expressed as gram per cubic meter or gram per Kilogram of air.

Absolute humidity can be expressed as Absolute Humidity = \(\frac{Mass of H_20}{Volume Of Air}\)

Relative humidity is defined as the ratio between the vapor contained at a particular temperature and the vapor that could have been contained at that temperature. Relative humidity is normally expressed as a percentage and can even exceed one hundred percent. If a system has a relative humidity of more than 100 percent then it is called a supersaturated system. 

Specific humidity can be expressed as the ratio between the mass of vapor and the mass of air that holds that vapor. As the temperature lowers down, the amount of vapor needed to attain the saturation point also lowers.

Ans. Temperature is a basic factor which governs both water evaporation and condensation. If we talk of an enclosed space where all other factors like wind, air, and sunlight have no influence at all, in such a case at a given temperature the air inside that room will hold a certain amount of water vapor. This in layman’s terms is called absolute humidity. As is clear from the name, the absolute humidity will rise with a rise in temperature. 

Absolute Humidity ∝ Temperature

But when we talk in terms of relative humidity, then humidity is inversely proportional to temperature. Relative humidity gives an approximation of the amount of vapor that is held in the air at a given temperature in relation to the total amount of vapor that could have been held.

Relative Humidity ∝ 1/Temperature

For an enclosed system, relative humidity depends on the absolute pressure. If we keep the temperature constant, the isothermal system, and apply pressure, automatically the volume of the system gets reduced, increasing the partial vapor pressure of the water molecules and thus increasing the relative humidity of the system. 

Ans. The human body has its own temperature regulation mechanism. So when the humidity changes, this temperature regulatory mechanism behaves differently. In more humid conditions some humans experience difficulty in breathing. Numbness, lack of concentration, and physical strength are some effects of high relative humidity. The human body can take a relative humidity in the range of 30 to 70 percent. Anything above that will affect the metabolism of the human body. Low humidity leads to respiratory problems.

Extreme levels of relative humidity can be dangerous in many ways. Too low humidity can cause irritation in the eyes, drying of nasal passages, etc. Higher humidity leads to anxiety and asthma. The solution for the problems associated with high and low relative humidity is addressed by humidifiers and dehumidifiers.

Ans. The air at the altitudes of air traffic is very cold and the humidity is very low. If the air gets warmer the humidity gets lowered down further leading to discomfort in travelers. Extremely low humidity may even lead to the formation of ice in the aircraft which can seriously affect its balance in the air. If the humidity inside the aircraft is increased using humidifiers then condensation-related problems may arise. To handle all this well certified equipment is used in the aircraft. High humidity also leads to aircraft requiring longer runways.