Humidity Control

There are many problems associated with the amount of humidity present in the atmosphere. Under the conditions of high humidity, the evaporation of sweat from the skin is decreased and the body’s effort to maintain an acceptable body temperature may be impaired. In warmer atmosphere where humidity is relatively high, blood brought to the body surface cannot shed any heat by conduction to the air, and a condition called hyperprexia results. A high humidity can also result to heat stroke. This condition refers to the decline on the capacity of the body to remain alert. High humidity can also contribute to mold production and dust mites.

In human body, it is recommended that a relative humidity should be kept between 30% to 60%. This is according to the US Environmental Protection Agency citation on ASHRAE Standard 55-1992 on Thermal Environmental Conditions for Human Occupancy. Humidity below 50% is said to prevent dust mites.

Humidity control is important for health reasons. Products are invented to remedy the problems associated with humidity. However, it is important to know some things about humidity.

What Is Humidity?

Humidity is the moisture content in the atmosphere. The atmosphere always contains some moisture in the form of water vapor; the maximum amount depends on the temperature. The amount of vapor that will saturate the air increases with a rise in temperature. When the atmosphere is saturated with water, the level of discomfort is high because the evaporation of perspiration, with its attendant cooling effect, is impossible.

Humidity has several specifications and measured in different ways. The weight of water vapor contained in a volume of air is known as the absolute humidity and is expressed in grams of water vapor per cubic meter. The ratio of the weight of water vapor to the total weight of air (including the water vapor) is known as the specific humidity. The ratio of the weight of vapor to the weight of dry air (with the water vapor removed) is known as the mixing ratio. Both of these, the mixing ratio and specific humidity are units in grams of water vapor per kilogram of air. If air expands or contracts, its absolute humidity changes but its specific humidity and mixing ratio do not.


Relative humidity, given in weather reports, is the ratio between the actual vapor content of the air and the vapor content of the air at the same temperature saturated with water vapor. If the temperature of air rises and no change occurs in its vapor content, then the absolute humidity remains the same but the relative humidity is lowered. A fall in temperature increases the relative humidity.

If air cools to the point that its relative humidity reaches 100 percent, then the air is saturated and can not hold any more water vapor. The air is said to have reached its dew point. If the air cools any further, then some of the water vapor will condense. If the air is adjacent to the ground, the extra moisture will condense into cloud or ice crystals and form clouds or fog. Under the proper conditions, rain, snow, sleet or hale may fall from clouds.

A humidity meter is called hygrometer. It is a device used to measure the humidity. Some humidity controls such as the humidistat is used to regulate the humidity of the building using de-humidifiers. It is analogous to thermostat, a device used to regulate temperature.

Humidity control systems have been advertised in the internet marketing recently. Humidity chambers are among the innovative products being manufactured to bring about solution to humidity problems. Dehumidifiers are also fabricated to meet the similar need.

Humidity controls have made a substantial effect in controlling the amount of water vapor present in the atmosphere. Using the devices for controlling humidity has helped people in dealing with some health concerns at home.