Sensgreen Knowledge Base

Humidity and Relative Humidity (RH)

What Is Humidity?

Humidity is the amount of water vapor in the air, and it is quite crucial for humans and should be tracked regularly to prevent the negative effects on both humans and the buildings. Similarly, relative humidity is the ratio of the water vapor in the air to the maximum amount of moisture that air can hold within the present situation. When you hear the humidity in weathercasts on TV, the numbers you see are actually the relative humidity.

itchy skin

Dry and itchy skin

runny nose

Respiratory tract problems

eye problems

Eye Problems

being susceptible to infections

Being susceptible to infections

Health Effects Of Humidity

Low levels of humidity can cause dry and itchy skin, eye problems, and respiratory tract problems. Low humidity levels allow the viruses in the air to survive longer than normal, and due to dry air, mucus membrane might get dry, which makes people more susceptible to infections, according to SOC health organization UK.¹

On the other hand, high humidity levels may also cause different problems for human health. When humidity reaches higher levels, it makes people feel the temperature a lot higher than it actually is. This will make your sweat glands work more to drop the temperature of your body to normal levels and maintain it, which can cause dehydration. Also, as the low humidity can cause the mucus membrane in your nose to dry, the opposite happens with high humidity. The increase in the amount of mucus can cause congestion, sneezing, and runny nose.

Humidity, Buildings and Mold

In addition to issues and symptoms on the human body, high humidity levels can also cause mold problems in the buildings. Facility managers should track and keep the Humidity levels (RH) below 60% in order to prevent molds from growing on the premises and ideally should be kept between 30%-50%. According to the EPA, keeping the humidity levels below 30% may also provide a solution against pests and dust mites. ²

Mold is a fungal growth and molds might cause both aesthetical problems on buildings and many health problems for people inside those buildings. According to CDC (Centers for Disease Control and Prevention), mold exposure does not always cause health problems; however, most people are sensitive to mold. ³

Also, high levels of humidity can cause microbes, dust, and mites to grow and these are especially crucial for people with asthma. HVAC systems have utmost importance when it comes to dealing with humidity issues since they can remove the access moisture from the air and release it to the outside.

Due to these reasons, humidity levels (RH) should be monitored continuously to prevent mold growth and its damage to the HVAC systems and provide a healthier indoor environment for the occupants inside the buildings.


Covid-19 and Humidity

Maintaining the relative humidity in the 40%-60% range in indoor spaces could help slow the spread of the coronavirus. Humidity can affect virus transmission in three ways. Studies suggest that higher humidity can enhance the body’s ability to fight off infection; that the coronavirus decays faster at close to 60% relative humidity than at other levels; and that drier air can lead to greater numbers of tiny coronavirus particles that travel farther and penetrate deeper into the lungs. Especially in winters, in addition to other strategies—masks, distancing, ventilation and filtration—raising the humidity is another layer of defense to consider. ⁴


Effects of Humidity On Human Comfort

People are generally more concerned with temperature than with humidity when it comes to their comfort. ⁵ For this reason, many buildings only control temperature, without minding humidity control. However, relative humidity has a large effect on comfort. Our sweat evaporates to regulate our body temperature and dissipate the internal heat.

The low relative humidity typical of many interior environments in winter leads to an average temperature of 21-23ºC, sweat evaporates and we feel colder than we really should at that temperature. On the other hand, in summer we find rooms that keep the air above the recommended maximum level of humidity for comfort, 40-60% R.H. (relative humidity) due to a lack of humidity control, our bodies are unable to evaporate the sweat we generate to dissipate our body heat.  Also, humidity affects the performance of HVAC devices. As humidity increases, the cooling capability and efficiency of HVAC systems decline significantly. ⁶


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