Understanding relative humidity (RH) begins with understanding two key aspects: RH and dew point temperature. The dew point temperature is the specific temperature where moisture in the atmosphere condenses in dew form on surfaces with a lower temperature. For most people, the most comfortable level of environmental RH is somewhere between 40% and 60%, but it can be comfortable at a higher percentage in colder temperatures. Specific applications often require other ranges to meet a particular specification or facilitate certain processes. In industrial applications, operations tend to specify dew point instead of percent RH.


Learn more about relative humidity, the importance of monitoring it, and how to control humidity in a building or facility.

What Is Relative Humidity?

Relative humidity measures the percentage of water vapor content in the air at a specified temperature. It is relative to the maximum possible amount of water vapor the air can hold at that temperature. 

Percent RH is proportional to temperature and very sensitive to temperature fluctuations. A stable system temperature will ensure the RH is also stable. Pressure changes also influence changes in RH. 

In general, the percent RH decreases when the temperature increases because the air volume is increasing allowing it to hold more moisture  Conversely when the air temperature decreases percent RH increases because the air volume decreases. Basic rules only apply to closed systems like environmental test chambers. There will be other factors that increase or decrease RH in other systems.


Importance of Monitoring Relative Humidity

To maintain a healthy and safe environment, percent RH must be monitored with a recently calibrated hygrometer.  Without control, high levels of humidity could lead to the development of mildew, mold, corrosion, and rust inside buildings. High humidity could also negatively impact the quality of end products in many processing facilities. These risks make it necessary to keep percent RH from rising to dangerous levels. 

Many potential issues can arise due to inadequate RH monitoring across a wide range of applications. As mentioned above the only sure way to determine the correct percent RH is with the use of a recently calibrated hygrometer.

Some Applications, but not limited to, are shown Below:

  • In a grow room — If the air becomes too wet in grow rooms, it may cause the buildup of mold, mildew, and rot on plants.  High humidity could also lead to more frequent maintenance requirements.
  • In printing facilities — Relative humidity must be tightly controlled in printing facilities, as excess or insufficient moisture can cause deformation of paper and cardboard, irregular drying times,  the inability of printing media to hold ink properly and effect registry to name a few.
  • In food packaging facilities — Dry food products such as flour, spices, and cereals require packaging environments with low humidity levels. Without stable humidity levels, these products will be susceptible to premature degradation. High humidity may also negatively affect the quality of final products and lead to product clumping that slows packaging equipment. 
  • In pharmaceutical facilities — High humidity levels could cause product clumping in pharmaceutical facilities, potentially leading to problems with measuring concentrations or shell/capsell texture.
  • In data centers — If the humidity is too high in a data center, it may cause damage to components such as electronics, printed circuit boards, electrical equipment, and soldered connections. It could also lead to electrostatic discharge and oxidation that could compromise equipment longevity and safety. High humidity can cause low voltage connection continuity possibly causing open circuits or false readings.
  • In indoor pool rooms and spas — Facilities with indoor swimming pools, spas, and hot tubs can easily develop mold, mildew, corrosion, and rust due to out of control high humidity. Specialized pool room dehumidifiers help control RH for optimal guest safety and comfort.
  • In freshwater and wastewater industries — Mold, mildew, corrosion, and rust may build up on condensable surfaces without proper humidity control.
  • Any application where the strict control of relative humidity or dew point is critical.


How to Control Humidity in a Room/Building

When trying to control humidity in a building, it’s important to realize that humidity typically rises and falls in response to current outdoor conditions. Moisture vapor passes through walls fairly easily, unless the walls are equipped with a non-permeable vapor barrier. Leaking window frame and doors, poorly insulated walls, and other untended openings in the building structure can allow moisture to invade living spaces. However, you can minimize the effects of outdoor influences by providing a non-permeable vapor barrier in the building’s walls and ceilings. Another way to get indoor humidity under control is to assess and correct wet basement walls and eliminate any standing water.  Standing water or weeping walls problems must be corrected first before dehumidification can be considered as a solution.

Relative humidity is inversely proportional to temperature in a closed space. For example, a closed room contains a certain amount of moisture. When the temperature rises, the percent relative humidity will fall. When that same room is cooled, the percent relative humidity will rise. During a hot and humid summer, air conditioning can remove some unwanted moisture and cool the indoor space—all while raising the relative humidity in the facility or building.

Understanding these concepts can help you more easily identify ways to balance the effects of moisture and humidity and maintain an ideal indoor environment for your needs.


Speak to the Dehumidification Experts at DCA

The right RH is key to maintaining a healthy, comfortable indoor environment. Knowing how to control relative humidity with the right products will help you keep your facility safe and in good condition.

At Dehumidifier Corporation of America (DCA), we offer a selection of dehumidifiers, remote condensers, control systems, and add-on duct heaters. If you need a reliable moisture control system for your building or facility, contact us today to speak with one of our representatives.

Topics: Dehumidifiers