How Can Airborne Transmission of COVID-19 Indoors be Minimized?
https://www.youtube.com/watch?v=jK6Cef5A8FQ

00:0 Hello everyone and thank you for joining us. My name is Amanda Kramer and I am the 
00:0 Alumni Engagement Program Manager at the University of Colorado Boulder 
00:0 Leeds School of Business. These are certainly trying times and here at 
00:1 CU-Boulder we have gathered our world-renowned 
00:1 faculty and alumni to provide frank and timely insights for life during and 
00:1 after the COVID-19 pandemic. Today is the final webinar in this COVID-1 00:2 related webinar series. Stay tuned for more information about our next webinar 
00:2 series which starts the week of May 18. For today's webinar we're excited to 
00:3 have Professor of Mechanical Engineering Dr. Shelley Miller here presenting on 
00:3 how can airborne transmission of COVID-19 indoors be minimized. A few 
00:4 housekeeping items before we begin first if you have any questions now or during 
00:4 the presentation that you would like to ask Shelley please send a question 
00:5 through the chat interface we will monitor questions as they are submitted 
00:5 and Shelley will respond to them at the end of the presentation. As a reminder 
00:5 for optimum audio quality we do have everyone on mute except for myself and 
01:0 our speaker. If you experience any technical difficulties during the 
01:0 webinar please notify us through the chat interface and one of our support 
01:0 specialists will touch base lastly a link to access the webinar recording 
01:1 will be sent to all registrants tomorrow along with a survey link and 
01:1 supplemental resources from today's presentation. Now I am so excited to 
01:2 introduce today's speaker Dr. Shelley Miller is a Professor of Mechanical 
01:2 Engineering and faculty in the Environmental Engineering program at the 
01:3 University of Colorado Boulder holding an MS and PhD in civil and environmental 
01:3 engineering from the University of California Berkeley and a BS and Applied 
01:4 Mathematics from Harvey Mudd College Dr. Miller teaches about and investigates 
01:4 urban air quality and works diligently to understand the impacts of air 
01:4 pollution on public health and the environment she is also an expert on 
01:5 indoor environmental quality including air cleaning technologies. Dr. Miller is 
01:5 a member of the Academy of Fellows of the International Society for Indoor Air 
02:0 and Climate. Dr. miller has published over 70 peer-reviewed articles on air 
02:0 quality, authored a chapter on indoor air quality in the environmental engineer 
02:1 handbook, is an active scientists on Twitter and publishers open access as 
02:1 often as possible. Welcome Shelley and thank you so much 
02:1 for being here I'm going to hand the webinar controls over to you now. Thanks 
02:2 for that gracious invitation to speak here today. I'm really thrilled to be 
02:2 able to do this and I wanted to share our perspective and my perspective 
02:3 representing all the scientists that are trying to understand airborne 
02:3 transmission and what we can do about it here to you today on this webinar. I'm 
02:4 going to cover three things today I want to show you some of the information that 
02:5 convinces us that there is an airborne transmission route for COVID-19. I want 
02:5 to hit a little bit on why we also are communicating clearly that crowded 
03:0 poorly ventilated environments are at most risk for transmission. And then what 
03:0 evidence-based controls we can use to implement our strategies for reducing 
03:1 transmission and keeping people safer as we all open up our communities. I want to 
03:2 start with this graphic so we have a similar understanding of what I mean by 
03:2 airborne transmission we can define three major routes of droplet exposure 
03:3 there's the direct spray route or the droplet horn route the long-range 
03:3 airborne route transmitted by small airborne particles and a fomite route or 
03:4 touching of contaminated surface. Now this direct spray route can be divided 
03:5 into two sub routes shown here in terms of size of particle and the destination 
03:5 of the particles. The two sub routes are what happens with larger expiratory 
04:0 droplet and then smaller droplet I and the larger droplets tend to drop out of 
04:1 the air quickly and they can land on surfaces or on a person standing near 
04:1 you and then the smaller droplet nucleic and then 
04:2 be inhaled close to the person that has projected the aerosol onto you. And when 
04:2 we talk about admitted from from an infectious person to a susceptible we're 
04:3 talking about it could happen with talking with breathing with coughing and 
04:3 with sneezing and then other activities such as singing this is basically in 
04:4 line with the definitions from the US CDC Centers for Disease Control and 
04:4 Prevention however they don't actually distinguish between these short range 
04:5 and long range airborne routes but this is important because we want to point 
04:5 out that long range transmission can happen through ventilation ducts or 
05:0 across very large distances so far we have not seen a publication in the 
05:1 scientific literature showing that this has happened so so we're still not clear 
05:1 on whether that's an option for COVID-19. But there's a lots of evidence to 
05:2 show that transmission um is happening close range in the short range and 
05:2 droplet form route. As well as a new definition I'm going to add here for you 
05:3 today. It's called the extended short range and that happens because of 
05:3 crowding and lack of adequate ventilation which I will cover in the 
05:4 next couple of slides. So this article that I just wrote and published in the 
05:4 Conversation talks more about the aerosols and the and the scientific 
05:5 understanding of where they come from and the sizes and what happens to them 
05:5 so I'm not going to talk about that today but this is a great reference for 
06:0 you to read and also to access all of the scientific articles that I've quoted 
06:0 as cited in this particular article so let's talk a little bit about close 
06:1 contact respiratory tract infections are among the top ten leading causes of 
06:2 death worldwide and close contact plays a critical role in many respiratory 
06:2 infections a study done by one of my colleagues looked at 
06:2 you know how much close contact are we having in a typical day and what does 
06:3 that look like and then this data is used in in other studies to understand 
06:4 transmission but what I like about this is that well most people spend time 
06:4 about 1/2 a meter apart. So we're always in pretty close contact or we were 
06:5 before this pandemic. The short-range airborne route is found to dominate at 
06:5 most distances study during both coughing and talking once we understood 
07:0 this close contact problem so that's this diagram from the previous slide 
07:0 that I wanted to highlight to you show this short-range airborne route is 
07:1 really what how you get exposed when you're close contact with somebody less 
07:1 than 2 meters which i think is where the six feet idea really hole it's true for 
07:2 this understanding and then the large droplet route really only dominates in 
07:2 this study that I'm just citing here when the droplets were really large 
07:3 larger than 100 microns and when the subjects are within 0.2 meters 
07:4 or while coughing. So understanding this gives us this information that well 
07:4 close contact is why we implemented social distancing and that's why this is 
07:5 a very traditional approach to arresting pandemics that we've used over hundreds 
07:5 of years. So on to why we think SARS COVID too has some airborne transmission 
08:0 happening the environmental data suggests this is a route and papers are 
08:1 coming out every day of environmental sampling showing that yes we can detect 
08:1 the biology RNA in the air and on surfaces where air has transported a 
08:2 virus to that location. So the first point is talking about the table on the 
08:3 right and this paper was just published and so it is now peer-reviewed and 
08:3 available but what it shows is that concentration of viral RNA in the air of 
08:4 COVID was detected in a Wuhan Hospital in other areas. And it was quite high in 
08:4 certain locations. For example they found it elevated in the patient room toilet 
08:5 area. And so that is also important so that's up here patient mobile toilet 
09:0 room it was quite high an intensive care unit some of the places where they 
09:0 removed apparel was also high and that that indicates possible a deposition on 
09:1 two surfaces and then a possible B suspension later they also found it in a 
09:2 department store and some outdoors and also you know so other locations 
09:2 especially patient rooms etc yes I cut off the top of the chart from the paper 
09:3 so that I can put it on this slide but you can access the paper online. So there 
09:4 were also I'm going to talk a little bit about the viral RNA I'll just mention 
09:4 briefly that the first paper that came out we were all concerned when they 
09:5 showed that the surface of the air outlets and in a room had violent 
09:5 already on it we thought oh no that's not good that's the first indication 
10:0 that was a few months back that it was airborne we also want to point out that 
10:0 SARS COVID-1 was shown to be spread through the air. And we have papers 
10:1 showing that that happened on airplanes in hospitals and in apartment buildings 
10:1 as well. I want to talk weekly now about the detections that happen in the 
10:2 Nebraska hospital this is a really well contained and well-designed facility to 
10:2 handle bio containment and they took a few patients probably like 13 patients 
10:3 from one of the cruise ships and harbored them here and helped them 
10:3 recover and so what they did in this facility was make samples both on 
10:4 surfaces and air. And the diagram on the lab shows the 
10:4 copies of RNA per microliter we covered where they looked at the sample and so 
10:5 you know they found it in all sorts of locations floor under bed miscellaneous 
11:0 personal items, phones, the toilet. In the last three are the air samplers where 
11:0 they had bedroom air samples and Hallway air samples. And the final one 
11:1 is personal air samples. Where the sampling was done right near where the 
11:1 person that is tending to the patient had the sampler on them and so that is a 
11:2 real indication of exactly what you're being exposed to while you're in the 
11:2 environment. And then I just wanted to show you the table on the right from 
11:3 that paper that shows which samples were positive by PCR and it showed that the 
11:3 air handling great was 80% positive and that's similar to the Singapore study. I 
11:4 just mentioned to you and that the air all air samples were 63 percent positive 
11:5 out of 19 samples and they were able to culture for viability 1/2 of the samples 
11:5 which is important as well because you can get viral RNA that's not active and 
12:0 we think between 1% and 0.1% of airborne RNA for viruses is viable so we also 
12:1 have compelling evidence to so significant transmission in crowded 
12:1 poorly ventilated spaces so most hospitals are very well ventilated they 
12:2 have very strict ventilation standards that they need to follow but there are 
12:2 also poorly ventilated spaces where we've seen transmission in Japan they 
12:3 saw them from close contact in fitness gyms a restaurant boat on the river 
12:3 hospitals and snow festival attended restaurants. For example we've seen ski 
12:4 chalet associated transmission in France and here in Colorado was where our first 
12:4 outbreaks happen was in the ski towns. Ski gondola transmission in 
12:5 Idaho as well. An assessment of one of these outbreak investigation showed you 
13:0 were 20 times higher more high likely to get the disease by being indoors 
13:0 singapura clusters from tourist shops, banquet dinners dinners, and to church. 
13:1 There was a church associated to a cluster in South Korea and Washington 
13:1 State and those three family clusters in an air-conditioned restaurant is what I 
13:2 want to talk to you about next because it's a really important case to 
13:2 understand airborne transmission. First I want to point out that ordinary speech 
13:3 aerosolize and significant quantities of respiratory particles and some people 
13:3 are what we call super emitter so they can emit orders of magnitude more 
13:4 infectious aerosol than another person and in you know in studies of the 
13:4 numbers of particles that's generated from 
13:5 coughing you know they're upwards of 300 thousand particles and then as low as 
13:5 about six thousand aerosol particles can be emitted in a ten minute conversation. 
14:0 And again by way a reminder from my previous point that the short-range 
14:0 airborne route is dominant during talking and coughing and then the large 
14:1 droplet is when you're talking but you have to be really close or really far so 
14:1 here's the case of the outbreak in the restaurant in China where we had an 
14:2 index patient here in yellow a one that was not showing symptoms of infection 
14:3 yet they came down with the disease either later that afternoon or early the 
14:3 next day and they had traveled to this location from Wuhan and then they ate 
14:4 because it was New Year's Eve celebration so they went to this very 
14:4 popular restaurant and ate at this table with their family members the outbreak 
14:5 happened with the joining tables these two tables B and C and they were not 
14:5 related in any way they didn't have any close contact with each table and they 
15:0 can tell that through the video feed of this event and they don't also 
15:0 see any of this with the serving staff they were very minimally in this space 
15:1 what did happen was that this air conditioner was blowing air and then 
15:1 pulling air back recycling it through this air conditioner causing the aerosol 
15:2 to be more widely distributed than otherwise and the ventilation rate in 
15:2 this space was almost non-existent. There is an estimate and a new draft paper out 
15:3 of the ventilation rate which is very low no windows were open and it was cool 
15:3 outside and there's no external ventilation only ventilation in this 
15:4 space would be through open windows and then they just cool the air by 
15:4 recirculation so we see the aerosol being transmitted right in this zone and 
15:5 none of the rest of the restaurants saw the exposure. 
15:5 I know people asked all the time about outdoor air transmission so I just 
16:0 wanted to mention briefly that are that this data here was talking about indoor 
16:1 transmission of SARS COVID 2 and they looked at 7,000 identified cases in 
16:1 China they only had one outdoor air outdoor outbreak involving two cases 
16:2 where they had a 27 year old man with a conversation and and also because they 
16:3 returned from Wuhan. So the graph below shows you the distribution of 331 16:3 outbreaks and what I find very interesting about this information is 
16:4 that most of the cases are transmitted by the family member that's or by a 
16:4 family relative the blue or orange or family member or family relative and 
16:5 then below is the social connection social mental connection and so a and B 
16:5 are different venues and highest again is that home or transport interestingly 
17:0 on the Left I just show the graphic from the modeling study that hasn't been peer 
17:1 reviewed yet but I vote for this researcher group and this institution 
17:1 doing good job this is a CFD simulation showing where the plume of aerosol could 
17:2 potentially go and so how much distancing you might want to do when 
17:2 you're running or riding your bike I also want to hit on the point that 
17:3 aerosols of SARS COVID-2 have been shown in the lab to have a half-life of 
17:4 one hour so they can if they stay over when they can't remain infectious for a 
17:4 while. And the half-life means it takes about how long it takes for the amount 
17:5 in the air to decrease by 50% the highest is on plastic and then again the 
17:5 tip time it takes for no virus for cardboard of 24 hours which is why I 
18:0 leave all my packages on my front porch for a day before I bring them in and 
18:0 then plastic and stainless chill and this is plastic is quite a long time 
18:1 which is why I try to wash all my plastic containers and air establish a COVDis in the fine aerosol which is one micron or around 1 micron 
18:2 particle size and by the way of context a human hair it's about 100 microns so 
18:2 you cannot see one micron particles with the naked human eye and they stay aloft 
18:3 for a couple hours depending on the indoor air currents. Onto evidence based 
18:4 airborne infectious disease controls. We are you're all hearing that you need to 
18:4 wear masks and I have highlighted the precautionary principle here which I 
18:5 don't know if I'll discuss briefly but the point is for masks you want to wear 
18:5 them if you are asymptomatic or possibly could be infectious because you don't 
19:0 want to infect other people from this potential and there are lots of data to 
19:0 show that you wearing a mask can really decrease the amount of aerosol that you 
19:1 transmit there there are the data are showing protecting you wearing a mask 
19:1 from another individual coughing on you does not you know it helps a little bit 
19:2 but it's not the real reason why you are you wearing a mask. Clearly we know - 
19:2 wash our hands and surfaces. Because it is on surfaces 
19:3 we also are highly recommending that you need to increase your outdoor event air 
19:3 ventilation rate and distribute it effectively. Do not recirculate. We also 
19:4 recommend air cleaning and disinfection devices and I'm only going to recommend 
19:4 two here these are the two areas of my expertise which is germicidal UV and 
19:5 filtration. And then if we minimize the number of people sharing the same indoor 
19:5 space we will reduce the viral loading and any unsuspected transmission so just 
20:0 talking briefly about the surgical mask. I'm sharing with you this data that came 
20:0 out recently about respiratory viral shedding with the Esaki efficacy of face 
20:1 mask while exhaling exhaling your breath on the left is showing the virus copies 
20:2 per sample of the people in the study and they looked and they were they did 
20:2 have virus in the nasal swab and a throat swab and when they used the masks 
20:3 then the droplet particles greater than 5 microns without masks was elevated and 
20:3 it went to very low detection limit when you wore the mask and so this is what 
20:4 you are and exhaling to other people and then the aerosol which is the small 
20:4 fraction that stays airborne is also released when you don't wear a mask but 
20:5 it's not released when you do wear a mask the type of mask here was not 
21:0 really clear but it's called surgical face masks so these are not homemade 
21:0 masks but there are surgical face masks which fit similarly to the homemade 
21:1 masks in my opinion. This diagram was shared by a colleague which I 
21:1 appreciated if you're standing closely and you don't have anything on either 
21:1 faces you're probably of getting sick it's quite high on the other hand if you 
21:2 have a mask on and you're infectious and you're standing the appropriate distance 
21:2 away you are really minimizing transmission and onto ventilation that 
21:3 we are recommending increasing clean outdoor air supply we're trying to 
21:4 figure out to what level you need to increase it 
21:4 right now using some modeling we think it's at least as higher than 10 liters 
21:5 per second per person other papers that have done a assessment of health effects 
21:5 from and from health effects from getting sick in buildings and what's the 
22:0 ventilation rate you need to reduce that could be upwards as high as twenty five 
22:0 liters per second per person and it's definitely clear that you're if you're 
22:1 down below ten or even one liters per second per person the risk of 
22:1 transmission is quite high so the data on the right shows how this was a modern 
22:2 study and I think it's from flu and they were modeling flu transmission so on the 
22:3 Left the y-axis is the percentage of daily infections and you can see here 
22:3 that as we increase the ventilation rate to seven air changes per hour which is 
22:4 the volumetric flow rate divided by the volume of the space we get a much 
22:5 reduced daily infections the lower graph I also like it's the attack rate showing 
23:0 that you can go to zero if you get above eight your changes per hour and a little 
23:1 bit about germicidal UV that's one of my areas of expertise and what I want to 
23:1 introduce to you about airborne about germicidal UV is first talking about the 
23:2 lamps so on the left is a diagram showing the output of the lamps and we 
23:3 commonly use low pressure mercury lamps and those are the ones on the right that 
23:4 are showing in blue light and and then the germicidal effectiveness is has been 
23:5 determined to be around 265 so you inactivate organisms 
23:5 at around to 65 nanometers wavelength. So 254 nanometers wavelength from a low 
24:0 pressure mercury lamp these lamps. If you're doing it right you install 
24:0 doped quartz glass which blocks the transmission of 185 nanometers which is 
24:1 where we would generate ozone so that's the small graph here this little purple 
24:2 diagram we do not want any ozone in our building you you get it from you know 
24:2 ionisers and bringing outside area that has lots of ozone but this is the 
24:3 wavelength of generate a zone the doped glass does not have any of this 
24:4 wavelength in it this is a UVC LED that's now in the market we don't use 
24:4 these for large applications like buildings because they just don't put 
24:5 enough power I want to point out that UVC has some adverse health effects if 
24:5 you're overexposed and we have exposure limits available from the Occupational 
25:0 Health and Safety Administration and we know you can get eye and skin irritation 
25:0 because the skin penetration is very shallow. It has not been shown to be a 
25:1 human carcinogen like a and b. And here's what happens when you irradiate a 
25:2 microorganisms you cause there's a couple of the thymine dimers to 
25:3 conjugate and then they are not this this D in RNA is not able to replicate 
25:4 so this is the application one of the applications there are three typical 
25:4 applications I'll just talk about this one for a couple of reasons it's called 
25:5 an upper room air disinfection where you hang the lamps in the unoccupied upper 
25:5 part of the zone so you know about seven or eight feet from the floor the 
26:0 occupants are in the lower part of the zone and lamps are designs 
26:0 the radiation is going across the room and not into the lower part of his own 
26:1 and then the generated virus has to circulate in through air currents 
26:1 through the irradiation zone to be inactivated and for most indoor spaces 
26:2 there is mixing in the space and so this does happen naturally the applications 
26:3 for this kind of technology would be in rooms in which infectious aerosol may be 
26:3 generated so you do see it in hospital as quite frequently. 
26:3 I've studied three applications in Denver hospitals a few years ago and 
26:4 there may be more now it's also recommended when you actually really 
26:4 need to increase your air changes but you can't do it by by changing your HVAC 
26:5 because it's just too costly and you can't retrofit your HVAC. So you can 
26:5 add the UV lamps to get additional air changes and this is where the CDC has 
27:0 recommended UV lamps to be very useful in increasing your air changes. Another 
27:1 place that I always advocate for UV is in crowded environments where 
27:1 unsuspected infectious persons may be present which is you know the case here 
27:1 with COVID where we don't know whose infectious and who's not. And it has been 
27:2 used quite a lot in jails especially in other countries like Russia. It's also 
27:2 been applied in homeless shelters in hospital waiting rooms so this 
27:3 technology has been around for a very long time and they used it in the 
27:4 earlier part of this century for trying to eradicate and keep keep the pandemics 
27:4 of measles mumps and chickenpox from spreading throughout throughout schools 
27:5 for example. So this physician install of UV lamps in two and three schools in 
28:0 Philadelphia and study the outcomes of the 
28:0 of these disease outbreaks for over six years I like the first sentence of his 
28:0 paper it reads the prevalence of respiratory infection during the season 
28:1 of indoor congregation suggests a natural relationship between ventilation 
28:1 and communicable disease so one of the outcome that has been reported from this 
28:2 particular study in 1943 was that this number of susceptible is infected was 
28:3 much lower in radiates primary classrooms compared to the Unrated 
28:3 primary classrooms despite the fact that there were more susceptible in the 
28:4 irradiated classroom compared to the Unrated classroom and there's other 
28:4 additional studies back in the 40s and 50s. 
28:4 For example they tried to use UVC in New York schools and I found that it did 
28:5 modify the spread of measles and chickenpox meaning it kind of changed 
28:5 the curve you know modify the curve which is what we're all trying to do 
29:0 right now by staying home so just a brief mention for example data showing 
29:1 why these are so effective when you install a system according to CDC 
29:1 guidelines you get upwards of 90 percent effectiveness applying these lights and 
29:2 you can get up to 17 additional air changes per hour which is what our 
29:2 studies showed I'm here at the University of Colorado. I do want to 
29:3 point out the importance of mixing here in the wintertime conditions where we 
29:3 introduced warm air at the ceiling you know most US buildings introduce air and 
29:4 exhaust air all in the ceiling and so if you introduce warm air and the ceiling 
29:4 gets stratifies in the room and then it causes the inability for bio aerosol to 
29:5 mix into the upper zone and here are some pictures of the lamp being used in 
29:5 a homeless shelter and in a hospital so we found this is another paper which I 
30:0 really appreciated they used epidemiological modeling to test 
30:1 different strategies for reducing pandemics and outbreaks 
30:1 and also implemented the effects of engineering controls including 
30:2 ventilation and filtration and UV and found that UV was the most optimal 
30:2 strategy with isolation and vaccination for containing flu measles and 
30:3 chickenpox. My last topic is air cleaners they really work but you have to know 
30:3 how to purchase the right one I'm only talking here about portable air cleaners 
30:4 the kind that you bring into your home if you're worried about exposure to 
30:5 wildfires for example which is what most of us have been worried about but now 
30:5 we're worried about exposure to to airborne virus the clean air delivery 
31:0 rate is how I recommend consumers understand and which which product to 
31:0 buy it will this is a test protocol that is well done by the yes sociation of 
31:1 home appliance manufacturers is supported by scientists and researchers 
31:1 and they test against dust tobacco smoke and pollen tobacco smoke is the kind of 
31:2 particle that probably is the same size as the airborne part of COVID and then 
31:3 dust and pollen would be the larger particle size for COVID. So this clean 
31:3 air delivery rate for this particular air cleaner shows that it can clean up 
31:4 to 100 square foot room so if you're trying to clean a 400 square foot room 
31:4 you're going to need three of these air cleaners in order for it to work 
31:5 effectively this is the air purifier if you want to know what I just purchased 
32:0 for my room in the basement where I will be isolated if I ever get this disease I 
32:1 have this airplane you're ready to start operating so it has a clean air delivery 
32:1 rate of two hundred and sixty and it's the maximum area for cleaning is about 
32:1 700 square feet it's the highest flow rate I could find it is pricey but but 
32:2 air you know you can get airplane that are smaller for about $200 and 
32:3 finally just showing you what what particle of sizes are removed in a 
32:3 filter the y-axis is the fractional efficiency and all of these numbers are 
32:4 the Association for heating ventilating and air conditioning engineers testing 
32:5 ratings and the highest rating number 16 is a HEPA filter which is the 
32:5 high-efficiency particulate and air filter. And I you know I do recommend 
33:0 considering that at this time even though when a recirculating mode you 
33:0 could get a non HEPA that would work okay so the hepa would remove both small 
33:1 and large particles due to particle dynamics that are you know too 
33:1 complicated here to be discussing but if you take my arrow subclass then I'll be 
33:2 able to explain why this happens so you can count on the small particles and the 
33:3 large particles and then it's a little bit less effective in the middle because 
33:3 of the dynamics of the particle size so in summary we have strong evidence for 
33:4 air broad transmission apologies for my dog and this is because we've sampled in 
33:4 the air and exhaust fence we know SARS was airborne and there's outbreaks among 
33:5 people who did not come into close contact the precautions against inhaling 
33:5 the virus are to physical distance yourself and increase your ventilation 
34:0 and filtration or germicidal UV if you need additional air changes and to treat 
34:0 the indoor air and then also I would be precautionary and wear a mask in case 
34:1 you're asymptomatic physical distance yourself wash your hands and frequent 
34:1 buildings that aren't well ventilated and this should say spend some time 
34:2 outdoors just not you know super close to people. Thank you! Please feel free to 
34:2 submit your questions and we will ask Shelley. Here let's start with a question 
34:3 from Paul. What is the most valuable thing that an indoor essential business 
34:3 can do to protect its employees? I would recommend first of 
34:4 take a look at whether you can increase your outdoor air supply and limit the 
34:4 recirculation happening in your building and then reduce the number of people in 
34:5 your building at any one time. Okay great and Mark asked is displacement ventilation 
34:5 an effective means of directing viral particulates to HVAC inlets and 
35:0 therefore exhaust or filtration? Yes it's a very good way to make sure that your 
35:1 air is both mixing and moving from the occupied zone up to the ceiling. Great. 
35:1 And then we have a couple of questions about the study that you referenced in 
35:2 terms of running or walking outdoors and having a runner or biker pass you what 
35:2 it's the compound factor of a breeze blowing toward both of us what is the 
35:3 recommended distance for runners or bikers? Yeah I can't sorry I don't 
35:3 actually remember that recommended distance I was I have a sense it's like 
35:4 three times whatever we recommend you know so maybe 18 20 feet but you'll have 
35:4 to refer back to that a paper to really to really check it out and I'd also like 
35:5 moving over. Like don't be right directly behind move over but check the paper out 
35:5 to get the exact distance. o Okay great and then opinion on air flow rates and 
36:0 buildings higher velocities may spread droplets further and counteract social 
36:0 distancing efforts what are your thoughts on this? 
36:1 Yes higher air currents do do allow the particles to move around the space 
36:2 faster and also deposit on surfaces faster. So that was the concern for the 
36:2 outbreak in China so I think you know making sure that you have adequate 
36:3 outdoor air coming into your space and maintaining a reasonable ventallation and 
36:3 reasonable velocity in your space for comfort I think that's a good strategy. I 
36:4 can imagine that if that if the restaurant had after air venhilation 
36:4 at all, the number of infections probably would have been lower. Okay great thank you. 
36:5 We have a question from Robert. Could you share what technologies are 
36:5 currently being used to detect the viral load? So there are most people are now 
37:0 doing genetic tests so they're doing quantitative PCR or they're doing some 
37:1 kind of genomic sequencing to rapidly determine what the what gene is being 
37:2 being discovered. Okay great and then a few questions. Milt is asking here about 
37:2 masks if cost masks absorb the water droplets carrying the virus from others 
37:3 can we still inhale the virus through the cloth could you tell us more about 
37:3 that? So there are studies looking at the 
37:4 efficiency of the material which is different than the fact that you could 
37:4 inhale an aerosol because your mask doesn't fit your face tightly 
37:5 that's called fit testing and that is very individualized everyone's face is 
37:5 different and I'm asked with it everyone different so we're always concerned 
38:0 about the aerosol going around the leaky areas and then also through the mask 
38:0 I would I would be more concerned with the fact that it goes around the 
38:0 surfaces of masks but there are data coming out showing what kind of material 
38:1 is most effective at reducing the transmission directly through the mask 
38:2 and I would say because you may have potential virus on your mask you should 
38:2 make sure you leave it sit for a few days before you be wear it or watch it 
38:3 and I just recently heard this study come out about actually putting you know 
38:3 a piece of elasticized material around the mask to keep it better fitted to 
38:4 your face. Okay great thank you for that. See we have another question here from 
38:5 Michael. What do you think of potential impacts of indoor RH on transmission? 
38:5 It's a tough question the reason I'm saying it's hard is because there are 
39:0 some evidence to show that at higher relative humidity viruses are less 
39:1 active but there's also some data showing that you know virus is suspended 
39:2 this particular virus or virus like this suspended in a respiratory fluid is 
39:2 there it's more insensitive to relative humidity generally with a virus we do 
39:3 think that higher relative humidity will decrease its activity but right now from 
39:4 what I understand what kovin it's being easily transmitted in high relative 
39:4 humidity countries as well as low relative community countries so right 
39:5 now we can't really say anything more definitive other than that. Okay thank 
39:5 you. Next we have a question from Peter. What 
40:0 about UV GI with in HVAC equipment is that as effective as the room based 
40:0 units you described? That's a really great application for for germicidal UV 
40:1 is to put lamps in the HVAC and that's typically has been used in the past for 
40:2 a variety of applications my my concern is to make sure you work with a good 
40:2 designer that can tell you the number of lamps you need to put in because you 
40:3 only have a few seconds for the virus passing through the UV zone to be 
40:3 inactivated and because of the different high velocities in the HVAC you know you 
40:4 can have a high velocity and not enough UV so that it won't do anything in our 
40:5 studies we've found in a couple of studies I've seen you know around two 
40:5 meters per second you can get effective inactivation but higher than that you do 
41:0 not because you don't have enough UV in the duct okay great thank you we'll take 
41:0 a couple of more questions this next one's from AG are there 
41:0 any recommendations for changing the direction of the vents and are there any 
41:1 special considerations for tropical climates no I don't have anything to add 
41:2 to that I mean I definitely think changing the events so they don't just 
41:2 blow down on people is probably the best suggestion at this time okay and then a 
41:3 question from Brian is needlepoint bipolar ionization technology in the 
41:3 HVAC system and effective solution there is a product that claims to not generate 
41:4 ozone so most of most air quality experts are more hesitant to recognize 
41:5 recommend ionizing air cleaning for a variety of reason including that it does 
41:5 generate ozone but if it's in HVAC it may have you know deposited onto 
42:0 surfaces and become have a minimal concentration by the time it gets to the 
42:0 room I don't know a lot of ionizing products also don't have it being enough 
42:1 and to treat the amount of air effectively so you know it's there's 
42:1 lots of reasons that filtration works great and air cleaning works great and 
42:2 then there are other reasons to say well we need to look at a little more closely 
42:2 so I I look at ionizing it's a little more closely and don't study that 
42:3 product so can't say too much about it. Okay thank you and we'll move in toward 
42:4 a final question from Steve. How long should we let coughs droplet nuclei 
42:4 settle before cleaning or disinfecting? 
42:5 Well I think if you I mean gosh if you're worried about people coughing and 
43:0 breathing and putting aerosol around you know it could settle within and out 
43:0 within you know tens of minutes or it could drop on a surface in an hour or a 
43:1 couple of hours so I would say you know multiple cleanings during the day as you 
43:2 go through your work day example is a really good strategy you 
43:2 know I'm hoping that people will be thinking that oh I need to clean for 
43:3 example at see you in the classrooms they probably need to clean these 
43:3 classroom surfaces you know multiple times a day well how are we going to do 
43:4 that because they do get contaminated quickly okay thank you for that 
43:4 information thank you so much to everyone for joining us for today's 
43:5 presentation and thank you again to Shelley for this great information as a 
43:5 reminder all webinar attendees will receive an email tomorrow with a link to 
43:5 the recording of this presentation to view upcoming webinars as well as 
44:0 previous recordings please visit our website at Colorado.edu/business/alumni 
44:0 We hope that you will join us during our next webinar series which 
44:1 starts the week of May 18th. In the meantime have a great rest of your day 
44:1 and go buffs!