Humidity and Viruses Focus of New Research

A new study shows the relationship between ventilation and viruses as well as between humidity and viruses. Using the Wells-Riley model helped researchers observe the effects of both humidity and ventilation on the SARS-CoV-2 virus. The study, set for publication in November, is the result of a joint effort among Scandinavian and Baltic researchers. It looks at the relationship between humidity and viruses as well as the effects of ventilation on virus transmission.

Humidity and Viruses

The model, developed to study the airborne transmission of tuberculosis and measles, is useful for studying the infection rates of other viruses. That includes the coronavirus. The model helps determine how susceptible to infection people are in a room with other infected people. The study found that ventilation plays a key role in controlling SARS-CoV-2 virus concentration in the air.

The model, while highly simplified, does reveal that humidification from 40% to 60% RH has a minimal impact on infection rates of SARS-CoV-2. Conversely, the model reveals that ventilation plays a much bigger role in reducing infection risk.

The impact of relative humidity and ventilation on the risk of infection depends on two factors. First, the size of the airborne droplets dispersed from the infected person. Second is the rate of outside air brought into the room. Researchers predicted that a change of RH between 20% and 53% would have little impact on infection rates. By contrast, they predicted that a change in the ventilation rate from 0.5 ACH to 6 ACH would cut the infection risk by half. Therefore, the takeaway for building managers is, steps to improve ventilation to reduce airborne virus levels keeps occupants safer.

Showing the relationship between ventilation, humidity and viruses help building managers and engineers reduce the risk of virus spread. 

Increasing Ventilation Key to Reducing Virus Spread

Pure Air Control Services helps reduce infection spread using systems and methods that improve indoor airflow.

HVAC Hygiene Assessment

An HVAC Hygiene Assessment is an effective way to gauge the impact of the HVAC system on indoor air quality. Improving the performance of the system through cleaning, disinfecting, and upgrading or replacing aging parts dilutes the virus concentrations in the air. This helps keeps workers, students, and visitors safe from infection and is more important than the relationship between humidity and viruses.

Mechanical systems become dirty over time and this degrades their performance. Consequently, it prevents them from lowering the potential impact of viruses. Our HVAC Hygiene Assessment provides a visual inspection of the air handling unit (AHU). This includes the ductwork, drain pan, blower, and evaporator coils. We also test for duct leakage and look at air filtration, building airtightness, and building pressure in addition to testing for bacteria and fungi. 

At the end of the process, facilities managers receive a detailed report along with recommendations on improving ventilation. Even as the link between humidity and viruses is not as strong, humidifiers do provide other benefits to the indoor environment.


After the assessment, we use our PURE-Steam system to remove viruses as well as mold, fungi, and bacteria. Afterwhich, the restoration of HVAC units includes the application of antimicrobial paint. This HVAC New Life™ process restores the system to like-new condition.


The final step in improving ventilation rates is through the use of the PURE-Duct cleaning This method gets deep inside HVAC ductwork where it knocks out dirt and debris. Once loose, an industrial-strength vacuum system with a HEPA filter removes the particles.

Focus on Ventilation Over Humidity and Viruses

While a relationship between humidity and viruses exists, the relationship between ventilation and viruses is much more important. Improving HVAC performance and getting more fresh outside air indoors keeps occupants safer than focusing on humidity. To learn more about how Pure Air Control helps schools, universities, and businesses improve IAQ, call us at 1-800-422-7873 or email us here.