Stopping COVID-19 spread indoors requires air motion
Two very timely and valuable articles about indoor air quality and COVID-19 recently appeared in The New Mexican. (“Improving indoor air quality is crucial for health,” My View, March 13; “Gauging air quality key as mandates end in U.S.,” Health and Science, March 14)
Both articles described the need for proper ventilation for indoor spaces during the coronavirus pandemic, especially with masking mandates ending for many indoor venues. This note details additional ventilation needs for air motion to disperse any COVID-19 cloud emitted by the sneezing or even exhalation of an unmasked infected person and describes the steps we have taken at First Presbyterian Church in this regard.
Outdoor air is free of COVID-19 and, with even the slightest breath of wind, quickly disperses and dilutes any virus-bearing breath or sneeze from an infected person. Indoor ventilation must also similarly provide air motion so no location in which people are standing or sitting has only still air; air motion allows potentially infected air to be replaced with fresh air brought in from the outside or filtered by air purifiers with HEPA or high-quality MERV filters, as described in the articles, to remove COVID-19 aerosol particles.
Experiments have shown the cloud of aerosols from a sneeze can extend up to 20 feet and can linger long enough to infect people nearby. Typical HVAC systems provide enough air changes per hour to keep carbon dioxide levels acceptably low. However, the air motion provided by the HVAC may be too slow to move a sneeze cloud past other people quickly enough to avoid infection.
A simple test to observe air motion is to separate the two plies of a typical facial tissue, hold one ply up to the air you are breathing and watch. If the facial tissue hangs still, the cloud from a sneeze may also remain motionless, which indicates that additional air motion is needed for COVID-19 safety.
In addition to requiring proper masking and social distancing, we took the following steps at First Presbyterian before returning to in-person services on July 4; the purpose of these steps was to make the sanctuary air more like outdoor air regarding quality and motion:
◆ Changed the sanctuary HVAC system operation to provide 100 percent virus-free outside air without recycle of any sanctuary air.
◆ Placed six low-noise vortex fans at the front of the balcony blowing just above the congregation to disperse and dilute any COVID-19 cloud from an infected person exhaling or sneezing.
◆ Installed two window fans in the balcony that can run as intake or exhaust fans depending on outside temperature. Operating during loud parts of the service such as when the organ is playing, these fans double the air circulation provided by the HVAC system.
◆ Placed four HEPA-filtered air purifiers in the chancel to provide protection for the choir.
We have taken similar virus-mitigation steps using air purifiers and oscillating fans in several rooms of our Childhood Development Center. Other Santa Fe churches also have addressed these issues. Every situation is different, requiring different approaches for COVID mitigation.