Evidence Links Temperature and Humidity to Virus Transmission

Note: do what’s right for your building.

It is important to note that controlling airborne infections is a complex practice and that recommendations can vary based on your building’s unique situation. Research suggests that the transmission of airborne viruses in indoor environments is affected by factors such as relative humidity and room temperature. The evidence is sufficient to conclude hot temperatures and moderate humidity levels can be effective in inactivating viruses.1

 

The link between our air and virus transmission

Viral infections are directly influenced by the quality of an environment’s air, so proper humidity and temperature control are of priority. Due to the simplicity and size of viruses, these agents are unable to survive long outside of their host, but damp humid air or improper temperature control can increase their rate of survival. Virus survival is also dependent on things like season, moisture content, wind conditions, sunlight, and the presence of atmospheric pollutants.

Low humidity levels can increase virus’s life span

COVID-19 is a respiratory virus that is lipid-enveloped.  These lipid-enveloped viruses will tend to survive longer at a lower relative humidity, usually between 20-30%2. This applies to most respiratory viruses, which are lipid enveloped, including influenza, coronaviruses (including severe acute respiratory syndrome-associated coronavirus), respiratory syncytial virus, parainfluenza viruses, as well as febrile rash infections caused by measles, rubella, varicella-zoster virus. Now, before increasing your humidity, it is important to note that conversely, non-lipid-enveloped viruses tend to survive longer in higher relative humilities, such as between 70-90%3. This means that you will need to do a thorough air quality test before coming to any conclusions on what to do next.

Findings are not always consistent across the various viruses. However, evidence suggests there is minimal survival for both lipid-enveloped and non-lipid-enveloped viruses at an intermediate relative humidity of 40-70%4.

High temperatures may deactivate viruses

Temperature can also play a role in reducing the chance of survival of airborne viruses. Typically – as temperature rises, the virus survival rate decreases. Some research suggests, in fact, that maintaining temperatures above 60° C for more than 60 minutes is sufficient to inactivate most viruses5.

In a study done by The Journal of Applied Microbiology, in which the effects of altered environmental conditions on the persistence of Francisella tularensis bacteria and Venezuelan equine encephalitis virus (VEEV) the following results were determined:

“Viability of test organism was assessed after contact times ranging from 30 min to 10 days. Inactivation rates of F.t. and VEEV increased as both temperature and/or relative humidity were increased.6

Temperature, like relative humidity, has been proven in some studies to reduce the inactivation of certain viruses. Maintaining proper temperature and relative humidity control are low cost, high priority items to consider when reducing the spread of COVID-19.

 

Ensure safe temperature and humidity with monitoring

Continuous indoor air quality monitoring is an effective way to track temperature and humidity levels over time. If you use a solution like qlair, you can track these levels with ease from the web or your smartphone.

Monitoring your indoor air quality not only allows you to measure and analyze these key indicators (temperature and humidity) for virus survival, but helps you track other components like the spread of particulate matter, fine dusts, and Volatile Organic Compounds (VOCs).

 

Conclusion

Controlling the spread of viral infections is a complicated issue that requires a 360° view of your building operations, current state, and future goals. Tackling things like an optimized temperature and humidity maintenance protocol is a great step, but there are far more strategies to consider when looking to reduce the spread of airborne infections within your building.

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