Every time you exhale, you release CO2 into the air. Since COVID is most often spread by breathing, coughing or talking, you can use CO2 levels to see if the room is filling up with potentially infectious exhalations. The CO2 level lets you estimate if enough fresh outside air is getting in.
Carbon dioxide in Earth's atmosphere is a trace gas. As of August 2020, the average concentration of CO2 levels outdoors was 409.5 parts per million by volume (or 622 parts per million by mass). Atmospheric concentrations of carbon dioxide fluctuate slightly with the seasons, falling during the Northern Hemisphere spring and summer as plants consume the gas and rising during northern autumn and winter as plants go dormant or die and decay. Concentrations also vary on a regional basis, most strongly near the ground with much smaller variations aloft.
Information from: NOAA Earth System Research Laboratory DATA - Trends in Carbon Dioxide: Globally averaged marine surface monthly mean data. LINK: https://www.esrl.noaa.gov/gmd/ccgg/trends/
To test the “freshness” of air in a room, you can use a CO2 monitor. First, test the outside background levels. Typically you'll see the outdoor range between 409 and 414, with higher concentrations in urban areas. Then test the air inside. A room that's well ventilated won't have the CO2 concentrations rise above 800 ppm.
When you put more people in a room for longer periods, the CO2 from their breath increases. Large air exchanges can help bring that number down. The key is making sure it never goes over 800 ppm. If it does, you should empty the room and disinfect the air.
Increase circulation of outdoor air whenever possible by opening windows and doors, using fans, etc. Do not open windows and doors if the temperature outside is too hot or cold. You should also keep windows and doors closed if they pose a safety risk to children using the facility.
If your facility is experiencing higher levels of CO2, talk to an HVAC (Air Conditioner) installer. Consider installing something called ERV or Energy Recovery Ventilation.
This is the definition of ERV from Wikipedia.
"Energy recovery ventilation (ERV) is the energy recovery process in residential and commercial HVAC systems that exchanges the energy contained in normally exhausted air of a building or conditioned space, using it to treat (precondition) the incoming outdoor ventilation air. The specific equipment involved may be called an Energy Recovery Ventilator, also abbreviated ERV."
How to Monitor CO2
To monitor the air, each room should have a continuous monitoring unit. There are affordable units for under $100. Some will keep a record to show the peaks and valleys, so you can figure out when levels are increasing. Search online for Indoor Air Quality Sensor that has CO2 monitoring.
Can you have virus-free air AND higher levels of CO2?
Here's where it gets tricky. If CO2 levels are low, then theoretically, you're getting plenty of air exchanges, and any viral particles are diminished. But there are other options.
Option 1: UV-C Lights Kill Aerosolized Viral Particles
Disinfecting the air can be done relatively quickly if CO2 levels are elevated. The Department of Defense found that UV-C lamps can kill aerosolized viral particles in as little as 90 seconds. We recommend running UV-C lights for 5 minutes when people leave or change rooms as a precaution.
Researchers from Tel Aviv University ALSO proved that UV-C light kills 99.9% of coronavirus in under 30 seconds. This is additional validation for anyone using UV-C lights to kill virus lingering in the air of public spaces. You can read the research paper here: UV-LED disinfection of Coronavirus: Wavelength effect
At WeBeFit, we run UV-C lights for 5 minutes in each pod after a client finishes their workout. That's to kill any viral particles lingering in the air. It can also kill particles on surfaces (that our disinfecting procedures might have missed) in about 90 seconds. Click Here for information on UV-C lamps.
Researchers have also found LED UV-C lights can also kill the virus fast. You learn more by reading this study: SARS-CoV-2 viability under different meteorological conditions, surfaces, fluids and transmission between animals
Option 2: Air Purifiers with Medical Grade Hepa Filters
The following two paragraphs are from an article titled "Can HEPA Air Purifiers Capture the Coronavirus?" by Tim Heffernann. (Updated July 9, 2020)
(Link Here: https://www.nytimes.com/wirecutter/blog/can-hepa-air-purifiers-capture-coronavirus/)
The virus that causes COVID-19 is approximately 0.125 micron (125 nanometers) in diameter. It falls squarely within the particle-size range that HEPA filters capture with extraordinary efficiency: 0.01 micron (10 nanometers) and above. Many media outlets have incorrectly stated that HEPA filters don’t filter below 0.3 micron and therefore could not capture airborne coronaviruses. That’s wrong. This NASA study of HEPA filtration is quite technical, but the graph on page 7 and the preceding paragraph do a good job explaining why HEPA filters are actually most efficient—almost 100% at 0.01 micron—at capturing ultrafine particles below the 0.3-micron HEPA test standard.
“The big thing with trying to say that a HEPA filter would do any good is whether you’re getting anything to the filter or not,” said Kathleen Owen, a consulting engineer with nearly 40 years of experience in air filtration. “If it turns out—and this is the big if; I’m not sure you should even mention it—but if there’s stuff that’s getting into the air, HEPA would catch it.”
At WeBeFit, we have added Medify Air MA-25 air purifiers with H13 medical-grade HEPA filters to each workout pod. These units filter 0.1 microns. This is to increase the number of times air is exchanged in each workout pod and POTENTIALLY reduce our clients' risk while working out.
Room purifiers and UV-C lights do NOT remove CO2 from the air.
While both those steps have been shown to eliminate the virus, they do not scrub the air of CO2. That means CO2 levels may increase in a building without putting the occupants at risk. If you're disinfecting the air with UV-C lights and keeping air purifiers running with medical-grade filters, there may be no viral particles circulating.
The goal is to make sure that at least 50% of the air entering an HVAC system is fresh air from outside. But with the two options discussed above, you can still provide some levels of safety until you're able to upgrade your HVAC system.
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