It is important to note that controlling airborne infections is a complex practice, and that the majority of the recommendations provided are contingent upon your building’s unique situation. Generally, the effectiveness of airborne viruses in indoor environments is affected by factors such as relative humidity and room temperature. Research suggest that high temperatures and moderate humidity levels are recommended for inactivating viruses.1
The Importance of Temperature and Humidity
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. Viral survival is also dependent on things like season, moisture content, wind conditions, sunlights, and the presence of atmospheric pollutants. Through continuous indoor air quality monitoring, you can track your building’s temperature and humidity and how it affects your indoor air.
In the indoor environment, the infectivity of airborne viruses is affected by factors such as relative humidity and room temperature.
So, while we will be covering basic principles for how to reduce virus survival with temperature and humidity control, it is important to be aware of your indoor air quality as a whole. Monitoring your indoor air quality not only allows you to measure and analyze these key indicators (temperature and humidity) of virus survival, but helps you track other components like the spread of particulate matter, fine dusts, and Volatile Organic Compounds (VOCs).
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 humidities, 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.
Again, it is imperative that you are doing a thorough analysis of your building’s status and needs. Findings are not always consistent across the various types of viruses, but there does appear to be general indication that minimal survival for both lipid-enveloped and non-lipid-enveloped viruses occurs at an intermediate relative humidity of 40-70%4.
Temperature can also play a significant role in reducuing the chance of survival of these airborne viruses. Generally speaking, as temperature rises, virus survival rate decreases. Some research suggests, in fact, that maintaining temperatures above 60° C for more than 60 minutes is generally 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. The good thing is that tackling strategies like proper temperature and relative humidity control are low cost, high priority items to consider when reducing the spread of COVID-19.
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, like COVID-19, within your building. If you’d like to learn more about ways to reduce the spread of this infectious disease, check out another article covering several air quality and HVAC strategies to protect your building here.