On January 17, 2022, Dr Martin Luther King Jr Day, as the Covid-19 “Omicron” variant rages across the US, I watched our #17 University of Illinois “Illini” and #4 Purdue Boilermakers face off with 15,544 fans in the State Farm Center sellout.
Can we attend large venue events safely?
What are the risks?
Read on to learn more about why I could safely attend such an event even though I knew many others would not be taking important precautions for their own safety. And find out if I became infected!
Deb and I attended the recent University of Illinois versus Purdue University sold out basketball game to see our “Illini” battle the Boilermakers, to air quality collect data, and to analyze the risk of attending large venue events.
I want out, too! At 70 years old, I am fortunate to enjoy good health, but as an old person my risk is high. Build Equinox’s Covid-19 research and our ability to predict Covid infection risk indicated that we could safely attend the event. But what about everyone else?
People are trying to resume “normal” living as Covid-19 continues to send virus-variant infection waves around the world. CDC rightfully deserves criticism for its ever changing “guidance”, lack of concise objectives, and inability to explain reasoning behind their vague guidance.
Here is a concise list of recommendations to keep indoor spaces safe that we published in our newsletter nearly two years ago ... they are as true today as they were then:
- Maintain carbon dioxide concentration at 800ppm or less (40cfm per person of fresh air for sedentary activities)
- Recirculate a similar amount of air through MERV13 or better filters
- Wear masks!
Why should we do those things? Read our May 2020 newsletter article for the reasons.
Deb and I attended the recent University of Illinois versus Purdue University basketball game because we love our Illini, and we knew we could attend safely even if others around us were not so careful.
I know vaccines and masks work, and I know why they work. We also know how to predict the probability of infection. Can one flip a coin and have heads come up 100 times in a row? Yes, but that’s not likely. Can I get infected even if I am tripled vaxed and wearing a high quality, snug fitting N95 mask? Yes, but that’s not likely either.
The amount of Covid (Omicron) infection in our community is high like it is everywhere, but you can move around safely with low probability of infection if you are triple vaccinated and properly masked. I hate masks, but until Covid is out of one’s community they are a necessity.
You can determine the odds of infection for any situation you’re likely to encounter. Classrooms, restaurants, houses of worship and other places can be visited safely. Our easy-to-use and easy-to-understand “Covid Safe IAQ Calculator” provides you with the capability to determine how many people, how much exposure time, how much ventilation, how much filtration, and the importance of masking for reducing infection transmission and infection multiplication. Our Covid calculator also provides other information such as sick day reduction (from colds and influenza), productivity, energy usage, and cost.
Illinois versus Purdue Results
Our Illini lost to the Boilers in a thrilling double overtime game, 96-88. Unfortunately, we may have lost fans to Covid, too, because of today’s inadequate ventilation standards, confusing guidelines, and strong resistance to self-protection.
A plot of carbon dioxide concentration for the State Farm Center shows an increase from a pre-game level of 800ppm to 2200ppm over the course of the 2 ½ hour game. Peak carbon dioxide level indicates a fresh air flow of 8cfm per person, in line with today’s inadequate building ventilation standards (ASHRAE 62.1-2019). Current ventilation standards for large venues recommend 7.5 cfm per person with another 0.06cfm per square foot of floor area (125,000sqft), for a total air flow of 124,000cfm. It sounds like a lot of air flow, and it is a lot of air flow, but it is not enough air flow to keep people safe and healthy.
Using the Covid Safe Space IAQ calculator, Covid infections can be estimated as a result of attending the basketball game. The plot shows infections for indoor air maintained at carbon dioxide concentrations of 800ppm (40cfm/person; our recommended air quality guideline), 1200ppm (20cfm/person), 1600ppm (13.3cfm/person), 2000ppm (10cfm/person), and 2400ppm (6.7cfm/person). On average, the arena’s carbon dioxide concentration was 1600ppm for the game.
The plot shows Covid infections within large venues without any vaccination or mask protection, and differing levels of vaccination and masking protection. Included are comparisons of the “Alpha” (original dominate variant in the US), “Delta” (dominate variant over the past several months), and the currently dominate “Omicron” variant infections without any vaccination or masking protection. The Alpha variant has airborne transmission characteristics similar to influenza. The Delta variant is twice as infectious Alpha, and Omicron is twice as infectious as Delta under similar environmental circumstances (exposure time, ventilation, occupancy, occupant activities).
Illinois was experiencing 30,000 new infections per day on January 17, 2022. Assuming a 5 day infectious period and an Illinois population averaged amount of infection (150,000 infectious persons in Illinois), 1.3% of Illinois’ populace is infectious. Assuming 1.3% of basketball fans are infectious, most unknowingly because many are asymptomatic, 200 infectious fans attended the game.
Holding the State Farm Center at 800ppm carbon dioxide concentration shows that 400 (Alpha variant) to 1600 (Omicron variant) Covid-susceptible fans would become infected. CDC recently announced a 38% efficacy for two shots of mRNA vaccines (Pfizer and Moderna), and 82% for three shots. Assuming Illinois is 60% vaccinated with 50% efficacy, Omicron infection transmissions are reduced from 1600 to 1100 fans.
50% fan face mask usage with 50% virus-filtration effectiveness reduces Omicron infections from 1100 to 600 fans at 800ppm carbon dioxide. Note that most cloth masks are less than 20% effective because they are often loose fitting and because common fabrics do not filter infectious, sub-micron size aerosols. At 1600ppm average carbon dioxide concentration with 60% vaccination rate (and 50% efficacy), 50% mask usage with 50% mask filtration efficiency, 1900 fans are estimated to contract Covid.
A red line on the infections plot is drawn at 200 infections. Conditions in the State Farm Center that result in more than 200 new infections have accelerated the growth of Covid-19. If new infections were held to less than 200 as a result of game attendance, the basketball game would not be contributing to the growth of Covid, but unfortunately that is not the case.
One of the most criticized comments from the CDC early in the pandemic was that masks are more effective than vaccines. That comment is true! N95 masks reduce the amount of contagion exhaled by infectious persons by 95%! N95 masks reduce inhaled contagion by 95%, too, for a combined contagion reduction of 99.75%, resulting in Covid transmission reduction much greater than today’s waning vaccination protection. But this message never seems to be effectively communicated by those in the CDC and others in public health. The only cases below the 200 new infection red line are the ones with effective mask usage (90%) and mask efficiency (90%).
For those of us attending the game with effective face masks and triple vaccinations, the probability of infection is about 0.2% in comparison to an estimated 26% chance of infection by those who do not take self-protection seriously. My actions have reduced my chance of infection to a level I am comfortable with for social interaction regardless of the actions of others. At this level of infection probability, I am unlikely to catch Covid and equally important, I will not multiply the transmission of Covid.
I tested the day before the game and three days after the game with the same result ... negative. Will I continue to stay uninfected? It’s hard to tell, but the odds are that if I continue to be diligent in wearing an effective face mask while Covid is in our community, I can continue going out in poorly ventilated environments with poorly masked individuals with minimal personal infection risk. And you can, too!
