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Dr. Richard Corsi Profile picture
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25 Dec, 5 tweets, 1 min read
1/ "To prevent the virus from spreading, companies that needed employees to return to in-person work put up plexiglass barriers, implemented daily temperature checks and required workers to wear masks while in proximity to others." What's wrong with this picture?
2/ Plexiglas barriers are not very effective at reducing transmission by aerosol particles. Temperature checks do not catch pre-symptomatic, asymptomatic, or symptomatic infectors w/o fever. Masks "while in proximity of others" = unacceptable. Masks at all times indoors.
3/ And we wonder why there are outbreaks in the workplace. LRRS = Layered Risk Reduction Strategy, not LRR Shortcut. LRRS must be done based on layered interventions that make scientific sense. Performance = sad. Almost a year in, folks. What will it take to get this right?
4/ Workplace. Universal mask wearing for everyone (only way to assure an asymptomatic infector is wearing a mask). Physical distancing. Increased ventilation (aim for 2x ASHRAE 62.1-2019 or more if possible). Improved filtration (to MERV-13 if possible) and/or UVGI. Just do it!
5/ Portable HEPA air cleaners w/ appropriate clean air delivery rate (CADR) (e.g., 300 cfm) in appropriate spaces, e.g., < 1,000 ft2 w/ ceiling height < 10 ft. Staggered work hours to de-densify where possible. etc. Just do it!

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More from @CorsIAQ

Dr. Richard Corsi Profile picture
23 Dec
1/ More results (year 1) of our Healthy High School PRIDE study. Here we show a cumulative distribution plot of average rebreathed fraction (RF) of air in classrooms during the occupied day. RF is actually converted to a percentage on the vertical axis.
2/ Note that a rebreathed fraction of 0.03 (3%), for example, means that 3% of every inhaled breath originated from the collective respiratory systems of others in the indoor space (including anyone infected with COVID-19).
3/ In my recent USEPA webinar on layered risk reduction strategies for schools I argued for a maximum RF < 0.008 (0.8%) for classrooms during this pandemic. That translates to an average CO2 concentration of less than 700 ppm.

Read 7 tweets
Dr. Richard Corsi Profile picture
23 Dec
1/ Plots from our Healthy High School PRIDE (Partnership in Research on Indoor Environments) project, a 4-yr USEPA funded study and intense analysis of 46 high school classrooms in Central Texas.
2/ Plot A shows air exchange rate in permanent and portable classrooms in the unoccupied setting (end of school day to start of next school day). The x is mean value and central line on bars is median. Variation shown via percentiles and min/max.
3/ The mechanical systems were off in plot A. All ventilation was via infiltration. Note much lower values and spread for permanent classrooms. Portable classrooms are connected directly to outdoors, leakier, and prone to greater ventilation by infiltration.
Read 6 tweets
Dr. Richard Corsi Profile picture
20 Dec
1/ @CDCgov has bought into layered inhalation dose, and therefore risk, reduction strategies. Pleased by this recognition, but not ready to shower the agency with adulation. The agency's credibility has taken a hit. I want to see a sustained effort of focus & doing right.
2/ My life has been about looking forward. But it is difficult not to reflect on where we would have been today had recognition of inhalation of virus-laden aerosol particles in both the near and far fields been recognized by @CDC 10 months ago.
3/ Future planning for the next pandemic or continued battle with SARS-CoV-2 must rely on continued innovation, but also on a deep forensics analysis of all of the failures (on so many fronts - not just @CDC) that fueled an inferno of infection in the US & elsewhere.
Read 4 tweets
Dr. Richard Corsi Profile picture
4 Dec
1/ This did not have to be.

Over 100,000 Americans currently in hospitals with COVID-19 and over 210,000 new cases today. We are converging on and will soon surpass the 9/11 death toll EVERY SINGLE DAY. And we are going to see a huge surge in the next several weeks & months.
2/ Hospital infrastructure is strained. Morgues have overflown. Front line health care workers are physically and mentally exhausted. This is a tragedy inside of a catastrophe.
3/ Despite all of this, too many people refuse to do what is needed to starve this virus of its hosts. Too many are too accepting of the death and devastation. Too many are fueling an inferno of infectiousness. It's all been said before, but ....
Read 14 tweets
Dr. Richard Corsi Profile picture
2 Dec
1/ I was asked in an interview today about the history of Indoor Air Quality. I surprised the journalist by starting about 1 million years ago with controlled fires brought into caves.
2/ There is evidence of early recognition of the importance of local exhaust, with fires placed below shafts to the outdoors. How many died from carboxyhemoglobin poisoning before recognition of the importance of ventilation?
3/ Perhaps we can ask the same question today but replace carboxyhemoglobin with COVID-19 and fire in caves with SARS-CoV-2 in (pick your favorite crowded and poorly ventilated indoor space).

Perhaps it is time we learn something from Homo erectus.

Just do it!
Read 5 tweets
Dr. Richard Corsi Profile picture
28 Nov
1/ Indoor Air Quality Matters

On average, Americans live to be 79 years old and spend 69 of those years INSIDE buildings. Of these 69 years, 54 are spent INSIDE our own homes.

I explain more in this 2019 presentation @AAAS.

2/ The air pollution that we breathe during our lifetime, even pollution of outdoor origin, is dominated by the air we breathe INDOORS.
3/ We can dramatically reduce our exposure to air pollution by reducing emissions from indoor sources, removing pollutants of indoor origin (ventilation & good engineering controls), & designing/operating buildings to reduce outdoor pollution from penetrating indoors.
Read 5 tweets

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