A must read if you are using #CO2 as a proxy for #ventilation/#IAQ: The ASHRAE Position Document on Indoor Carbon Dioxide by the experts including Drs. Persily, Mandin, Kipen, Lau, Sekhar, Ms. Lan Chi Nguyen Weekes @WBahnfleth @WargockiPawel ashrae.org/file%20library… "This position document discusses the role of indoor #CO2 in the context of building ventilation and IAQ based on ASHRAE’s long involvement with those topics as well as the interests of its members and stakeholders."

I keep wondering...why have so many (schools) thrown $$$ at ionization without any scientific evidence that it works, yet are scared of upper room UV lamps because it might be installed/maintained wrong; but there is solid science behind UV for disinfecting air. We know how to do this. The first test was by some infectious disease docs wanting to disrupt measles transmission in schools. So they installed upper room UV. Guess what?

“this virus is one of the easiest, by far, to kill with UV light,” said senior author Karl Linden, #CUBoulder professor of environmental engineering.
colorado.edu/today/2021/10/… “It takes a very low dose. This indicates that UV technology could be a really good solution for protecting public spaces.”

Very interesting study just published! Airborne SARS‐CoV‐2 surveillance in hospital environment using high‐flowrate air samplers and its comparison to surface sampling onlinelibrary.wiley.com/doi/full/10.11… findings show air sampling as a successful tool for environmental surveillance of airborne SARS-CoV-2 in hospitals

Check out our great new paper led by Dr. Wagner: Modeling the impacts of physical distancing and other exposure determinants on aerosol transmission. Glad to be a part of this analysis, with amazing colleagues Drs. Sparks, Chen, Waldman and Dr. Macher oeh.tandfonline.com/doi/full/10.10… a particle size-dependent aerosol release model was developed to assess impact of near-field transport of infectious aerosol. This is essentially what is happening when you are standing close to someone that is infectious...

Measurements and Simulations of Aerosol Released while Singing and Playing Wind Instruments.The preprint of our paper is now available! scholar.colorado.edu/concern/articl… Our amazing research team includes @marinavance @mspede @Don_Milton @James_Weaver_83 ABSTRACT: Outbreaks from choir performances, such as the Skagit Valley Choir, showed that singing brings potential risk of COVID-19 infection. There is less known about the risks of airborne infection from other musical performance,

1/ ICYMI paper on variant linking epic and genetic data: imperial.ac.uk/media/imperial… 1. the variant does appear to be more transmissible. From my read of the paper, it accounts for about a half to 2/3 of an additional infection per every additional transmission. 2/ SO for example if I have COVID and I give it to my husband, highly likely, then if I had this variant, I might also give it to 1/2-2/3 of another person - which is not physically possible, of course!

1/My public comments to the @BVSDcolorado board meeting on 12/8. I am an engineering professor @CUBoulder and an expert in engineering controls for airborne infectious diseases. @DougChem @epibuff 2/I was instrumental in helping CU Boulder open its campus safety. we have had ~50 cases of COVID-19 positive students in the classrooms and not a single case of transmission.

1/13 MOST HOMES ARE POORLY VENTILATED. WHAT DOES THIS MEAN FOR COVID-19? Most homes in the US are are poorly ventilated. There is no mechanical system supplying outside air indoors and exhausting indoor air outside. Read the entire post here: shellym80304.com/2020/11/02/mos… The way homes are typically ventilated is by opening a window and/door, or by air leaking in (or infiltrating) through unintentional openings and cracks in the building shell. Homes recirculate indoor air through coarse filters when the heating or cooling system is operated.

1/5 The bottom line is that on school openings many districts are still operating as if it were Mar not Oct. In Mar most of us did not know how the virus was transmitted (too bad WHO did not tell us in Feb). Now we know & we know what do to do minimize airborne transmission 2/5 The goal is not to suppress every single case, but construct our indoor environments to minimize the potential for large spreading events. Schools can be safe low-risk spaces if they are following our (@linseymarr @j_g_allen @jljcolorado @CorsIAQ) recommended protocols.

1/4 Just so you know: my entire motivation for talking about how COVID is transmitted is to keep people safe. If it was clearly transmitted via fomites, then I would be talking about washing your groceries. And that is what I would be doing (I am not) 2/4 If it was only transmitted by large spray droplets then I would focus on supporting efforts to get acrylic partitions and shields on everyone. (and I would have a shield but I don't, I do wear glasses/googles with my mask)

Dear colleagues,
I am hiring a postdoctoral researcher for a new 3-y NSF project. The short version of the position is below and the longer version is described at this google form. Applications are accepted via this form also.
forms.gle/71B8hFHoiVw2DD… "Postdoctoral Researcher position available in the Miller Research Group to lead a 3-y NSF funded project at the University of Colorado Boulder and work with a cross-disciplinary team of engineers, computer scientists, sociologists, community members and community organizations."

1/4 Riley et al in 70s assessed measles outbreak in a NYC school, from a 2nd-grader and spread to 60 pupils. Data on ventilation rates, time spent in classrooms, and air samples were collected. They modeled using Wells-Riley equation the probability a student would get infected. 2/4 Here is the graph showing the Probability of Infection versus ventilation rate. (source: smartairfilters.com/en/blog/poor-r…)

This emission rate matches the range measured directly in the exhaled breath condensate of patients. Evidence suggests that ratio of gene copies to infectious virus is roughly 10^3 so the emission rate of 10^6 gene copies/h would correspond to 10^3 infectious virions emitted/h. This compares favorably to the quanta emission rate if the infectious dose is close to 1 plaque forming unit (PFU). We do not yet know the dose-response relationship for SARS-CoV-2, but prior work indicates that the dose of SARS-CoV corresponding to illness in 10% and 50% of

1/4 UV air disinfection is a good technology & useful for creating safer indoor environments during this pandemic. I fully support its use. (e.g.I recommended that a local correctional facility, a good application, look into its use as a means to control spread of COVID.) 2/4 I have given webinars and speak often about how upper room UV and in-duct UV are great technologies for many applications where there is crowding, unsuspected infection present etc. shellym80304.files.wordpress.com/2020/05/isiaq-…

1/2 Administrators, faculty, staff etc have done our part to get @CUBoulder ready for opening Aug 24. We have worked hard to reduce the risk of transmission and make our campus safer for our community. 2/2 the residents of Colorado have done their part to social distance and wear masks. The @GovofCO has done his part to require masks and we here in Boulder are committed to wearing them. Our case numbers are falling.

1/Here is my take. I was panicked back in March when COVID hit because I did not understand the transmission route and how to reduce my risk of getting this disease. Now I do understand. 2/I am sending my kids back to hybrid school 2 days a week because I live in Colorado and we have a sane Governor who declared a state-wide mask mandate. If you are visiting my state you better be here with a mask and you better wear it - or go home. @GovofCO

(1/4) This is one of my favorite classic papers that discusses the concentration gradient around a point source of emissions. In the COVID-19 era this would = an infected person emitting virus-containing respiratory particles. tandfonline.com/doi/pdf/10.108… (2/4) Results show that the average concentration at arms-length from the source is double the background concentration in the room. The near-source concentration = far field at about 1 m away.

(1/5) from @jljcolorado: "There is much evidence that COVID-19 has a substantial aerosol component in its transmission. But it is much less contagious than measles. (2/5) Therefore we expect the highest transmission at close contact, because that is where the aerosols are most concentrated.

(1/n) 10 days into our 6-mo study of the aerosol generation from musicians and performers and we have completed some exploratory experiments. Refining our approach continues and includes flow visualization, aerosol measurements in a test chamber and CFD modeling. (2/n) Project team: me (PI), Dr. Hertzberg, @marinavance, Dr. Toohey, Dr. Patel, Mr. Kumar and Ms. Stockman (@CUEngineering); Dr. Srebric, Dr. Zhu and @Don_Milton (Univ of MD)

(1/4) it may feel scary that transmission can occur by inhaling small airborne virus containing particles, but this knowledge actually gives you more power to make informed choices about how you spend your time and where. (2/4) Choose to be outside over inside; To wear a mask indoors or when close to people for an extended period of time, talking or singing or other respiratory functions.