1/ Simple answer = very little for aerosol particles but possibly (in some cases) dispersion that reduces close contact dose. But depending on flow conditions, there can be a low pressure zone on the downstream side that leads to some accumulation of particles.
2/ The risk of people letting their guards down thinking that barriers are somehow effective for aerosol particles is much greater than any benefit, IMHO. Technical answer next.
3/ Is there a benefit in terms of far field exposure? Very minimal. Here's why. Indoor aerosol particle decay rates (k) to (integrated) indoor surfaces range from approx 0.2 to 10/hr for 0.3 to 10 um particles, respectively (higher for larger diameter particles).
4/ k = vd x (A/V). vd is a deposition velocity, which is a function of particle diam, mixing conditions in bulk air, friction velocity near surface, and more. A = surface area. V = volume of interior space.
5/ Assuming that the barriers do not affect volume or deposition velocity (they might affect mixing and therefore could affect vd to some extent), then the key parameter is surface area, A.
6/ It does not appear to me that these barriers constitute more than a few % of the total surface area in the space (including walls, floor, ceiling, furnishings, & people when present) and would therefore lower particle decay rates by a tiny amount.
7/ In that context, it would probably be more effective to put patches of carpet on walls or fleecy materials hung from the ceiling to increase particle decay rate to materials with large surface areas (which I am not advocating).
8/ I am still not a fan of going to indoor restaurants right now because of the need to remove mask & because some (many?) will not be fully vaccinated. But the way to substantially reduce COVID-19 infection is not with barriers that (on average) have a minimal (if any) effect.
9/ The way to do it is to GET FULLY VACCINATED, wear a mask when not eating, minimize time in space (take out best) & for restaurants to increase ventilation & use one or more of: advanced central filtration, HEPA filtration systems, appropriate upper-room UVGI.

• • •

Missing some Tweet in this thread? You can try to force a refresh

Keep Current with Dr. Richard Corsi

Dr. Richard Corsi Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!


Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @CorsIAQ

3 May
1/ Ozone emissions from some electronic air cleaners.
On average, approximately 50% of ozone of outdoor origin is breathed indoors w/ some variation by city and building stock. Related indoor exposures are associated with mortality. pubmed.ncbi.nlm.nih.gov/22100611/
2/ Our team estimated health benefit-to-cost ratios associated with reducing indoor ozone of outdoor origin in 12 US cities and predicted high ratios for many types of buildings, including schools (substantial reduction in health effects/absences). tandfonline.com/doi/abs/10.108…
3/ So, despite typically being at much lower concentrations than outdoors it appears that indoor ozone of outdoor origin is important. It is confusing then that some would assume that indoor ozone associated with indoor sources is not all that important.
Read 8 tweets
24 Apr
1/ Inhalation dose occurs in both the near field (close contact) and far field in the same indoor space. It is reasonable to assume that near field concentrations in the breathing zone are < 2 to 8 x the far field based on measurements & modeling.
2/ The actual magnifier depends on distance, whether and type of masks worn, mixing conditions (TKE) between infector and receptor, mode of emissions (cough vs. speak vs. breath), body orientation of infector & receptor and controls in the far field.
3/ Assuming the magnifier is 4 x, then 15 minutes in close contact with an infector is the same as 60 minutes in the far field. In each case the dose is the same and the probability of infection from those doses should be the same.
Read 7 tweets
18 Apr
1/ From 2008 to 2010 I was honored to hold the Otto Mønsted Visiting Professorship at the Technical University of Denmark. @WargockiPawel was a wonderful host, shown here in a moment of utter coolness.
2/ I also had the good fortune to overlap one of my visits with @CJWeschler, @LouiseBWeschler, & Bill Nazaroff. Charlie, Bill & I gave a trio lecture by the "Three Amigos". Photo courtesy of @LouiseBWeschler.
3/ Two of my PhD students (Erin Darling & Clement Cros) @ut_caee visited & we did expts related to perceived air quality using human panels exposed to a number of polluted & clean air streams flowing over clay-based plaster. Remarkably positive impressions of clay-treated air.
Read 4 tweets
6 Apr
1/ Outdoor education. This time of year and for the next two months many schools have an opportunity to have some class periods outdoors (weather, space, and local conditions permitting). Do it if you can.
2/ A very nice whiteboard on wheels costs roughly the same as an XLNT HEPA filtration system on wheels, about 2 Grande Frappuccinos per student per yr for a class of 25 students. An investment of $10/student for each is small given$15K cost of educating 1 student/yr in US.
3/ I used to occasionally teach outdoors as a faculty member at the U of Texas at Austin on nice fall and spring days. Students would bring towels to sit on. It was a wonderful way to teach, and the students seemed to like it as well.
Read 4 tweets
5 Apr
1/ Great study. I used the results from this study and follow-up tracer experiments in restaurant X to estimate ranges of the volume of particles deposited in the respiratory systems of those infected.
2/ Results suggest as low as 1 picoliter (pL) (one-trillionth of a liter) and as high as low teens of pL for respirable particles (less than 4 microns in diameter) (greater particle sizes also modeled but volume mode is in particles less than 4 microns).
3/ This volume range was used to develop a new factor (omega) for simulations in other indoor environments, where the infector in Restaurant X is placed in a a gym, classroom, ride share vehicle, etc., and omega = inhalation dose in those settings divided by that in Restaurant X.
Read 8 tweets
29 Mar
1/ Ozone has been regulated in the US for 43 years due to its adverse impacts on respiratory health. The image on the right shows a healthy lung tissue (top) and lung tissue exposed to ozone at only 20 ppb during four hours of moderate exercise. .....
2/ On the top image, the cilia on epithelial cells stand upright and orderly. This is important for clearing mucous that may convey deposited particles, including those that may contain pathogens. Bottom image ...
3/ In the bottom image the cilia look less ordered, less upright, and the epithelial cells appeal distorted. The arrows point to neutrophils, indicative of inflammation due to inhalation of ozone.
Read 5 tweets

Did Thread Reader help you today?

Support us! We are indie developers!

This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal Become our Patreon

Thank you for your support!

Follow Us on Twitter!