Many people think that regulating the temperature in their environment is all that's required to create comfortable conditions. Not so! There's another factor that is directly responsible for how hot, cool, or "just right" the body feels: humidity. The humidity percentage is essential information for weather watchers as well as musicians, wine connoisseurs, woodworkers, health care professionals, race car mechanics, and gardeners.

While humidity may be expressed as "absolute," "specific," and "relative," relative humidity is the measurement used in forecasting weather. Calculated from 1 to 100%, relative humidity is the ratio of the actual water vapor in the air compared to the water vapor capacity of the air. If the relative humidity is 33%, the air contains about one-third as much water vapor as totally saturated air at the same temperature.

The human body has limited ways to adapt to climate changes in order to maintain a level that is both comfortable and safe. One method the body uses to stay in its comfort zone is by sweating. When the body becomes too warm, moisture moves to the skin's surface; when it evaporates, the body temperature is lowered. However, when humidity is high, cooling the body by sweating becomes difficult as high levels of water vapor in the air reduce the effectiveness of perspiration. Since air temperature and humidity together affect the rate the body loses or gains heat, the lower the humidity, the higher the temperature may be while the body stays in a comfort zone, and vice versa.

High humidity not only makes it hard for the human body to evaporate perspiration, it makes it hard for any moisture to evaporate in the air. Humidity levels of about 60% and higher can become problematic to home furnishings. Walls may show signs of mold and fungi, wallpaper can start to peel, and iron may start to rust. High humidity also provides a great environment for dust mites and mildew. Accumulation of moisture indoors assists with mold growth that could result in health complications.

Low humidity levels can also be detrimental to health and surroundings. Humidity levels below 30% can make breathing difficult, dry out mucous membranes, and cause skin irritations. Such low levels of humidity also increase static electricity that can cause problems with computers and printers. Extremely low humidity also provides conditions for allergens to remain airborne, thereby aggravating allergies and asthma.

Since both high and low humidity levels can have such a strong impact on body comfort, health, and surroundings, regulating humidity in your environment is critical in creating optimal conditions. The ideal comfort level is between 30-50%. You can use a hygrometer to track the humidity readings in your home or workplace. The addition of a humidifier or a de-humidifier can help you regulate your home's comfort zone.

Digital hygrometers utilize a sensor that changes its electrical properties based on the humidity. This change is converted electronically to a digital display.

Analog or dial instruments use a de-oiled human hair or a synthetic hygroscopic material that expands and contracts based on humidity. Through a mechanical linkage, this expansion and contraction turns the indicating needle.