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COVID-19 NFHS Study Update

As of today (April 19th, 2021), we have some important updates on the current state of the COVID-19 pandemic and congregational singing. Many of you will be aware that a large number of public education organizations have been sponsoring a scientific study out of the University of Colorado Boulder and the University of Maryland. That study has just released another update on their findings and updated their recommendations. Below is a link to the full paper, important excerpts that pertain to congregational singing, and my personal summary of the new information.


Full Paper Link

NFHS Scientific Study Prepress Paper (40+ Pages) (April 15th)

Important Excerpts

  • Using masks greatly reduced the aerosol concentration measured in front of the source. Plumes from talking, singing, and performing musical instruments were highly three dimensional and vary considerably in time and space. The plumes decayed rapidly and are highly unsteady, which lead to large variations in our plume-level measurements. In addition, our flow characterization data show that when masks were used, plumes were shorter and plume velocities decreased, which decreased the trajectory of highly concentrated jets of aerosol.
  • CFD modeling showed differences between outdoor and indoor environments of singing and playing the clarinet without masks. In an outdoor environment, ambient wind breaks the musician’s thermal plume and expelled airflow and accelerates the dilution of aerosol. In an indoor environment, the musician’s thermal plume and expelled airflow contribute to the spread of aerosol due to space confinement. In addition, the indoor walls force the formation of smaller eddies, and the consequent distribution of the particles. To minimize infection risk to musicians and audiences via aerosol, this study showed lowest risk with an exposure duration less than 30 minutes for indoor singing and clarinet playing, and an exposure duration less than 60 minutes for outdoor performance.
  • Face shields are only effective at close range to stop large droplets (such as the visible droplets from a cough or sneeze) and do not prevent aerosol from being emitted or inhaled. Much of the respiratory particles emitted are small in diameter and follow streamlines around face shields.
  • Performers should follow social distancing protocols as recommended by the CDC for music activities. Aerosol concentrations are highest closest to the source, both inside and outside, and decrease with distance.
  • If indoor spaces are used, we recommend having at least three air changes per hour in the rehearsal room and limiting rehearsal time to 30 minutes at a time before leaving the room for at least one air change. For a room that has three air changes per hour, one air change is 20 minutes.


My Recommendations/Summary

  • This new information reinforces the importance of proper mask-wearing.
  • In general, outdoor events are significantly safer than indoor events.
  • This new information reinforces the difference been shields and masks. Shields do not protect the wearer or other from aerosol transmission.
  • Air circulation, distribution, and “air changes” are key components to virus spread through aerosols. However, air circulation and distribution are unique to each building and room and highly effects how much and where aerosols may spread. Unless you have an airflow expert analyze your rooms, this is a big variable that makes comparing situations between churches nearly impossible.
  • The authors of this study are not recommending any distancing beyond what the CDC recommends. The current CDC recommendations for communities of faith (found here) are the same as their general social distancing recommendations: 6 feet.
  • These recommendations remain true for fully vaccinated individuals as per the CDC guidelines for fully vaccinated people here.


For more updates and resources on COVID-19 and congregational singing, please go to:

This update is written by Center Director Brian Hehn and should be used only as general advice in consultation with other trusted sources. This is his personal summary of the data presented and should not be considered scientific fact nor medical advice.