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FAQs on Protecting Yourself from Aerosol Transmission

The goal of these FAQs is to provide information to the general public in an efficient manner about how to prevent aerosol transmission of COVID-19, with the hope that this will allow more informed decision making by individuals or organizations.

It includes info about face masks and prevention of the infection. Face coverings (such as N95) can be useful for disease control alongside social distancing. Wearing face covering can help if you have coronavirus symptoms (such as coughs or sneezes) and is always better than no face mask.

Other topics include: is coronavirus airborne, are covid masks safe, droplet precautions, airborne precautions, coronavirus masks, different types of close contact.

These FAQs should always be similar or more stringent than information provided by Centers for Disease Control and Prevention (CDC), World Health Organization (WHO), and most regional & local health authorities.

coronavirus, guide, masks, healthcare, coronavirus masks, airborne precautions, N95


FAQs on Protecting Yourself from COVID-19 Aerosol Transmission

Shortcut to this page: https://tinyurl.com/FAQ-aerosols

Version: 1.78, 1-Oct-2020

Click here to jump over the scientific & historical details and go straight to the recommendations,

Click here for automatic translation into many languages (choose your language from the menu)

0. Questions about these FAQs

0.1. What is the goal of these FAQs?

0.2. Who has written these FAQs?

0.3. I found a mistake, or would like something to be added or clarified, can you do that?

0.4. Are these FAQs available in other languages?

0.5. Can I use the information here in other publications etc.?

1. General questions about COVID-19 transmission

1.1. How can I get COVID-19?

1.2. What is the relative importance of the routes of transmission?

1.3. But if COVID-19 was transmitted through aerosols, wouldn’t it be highly transmissible like measles, and have a very high R0 and long range transmission?

1.4. When you say that the resistance to aerosol transmission is rooted in history, what do you mean?

1.5 Are all infected people equally contagious?

1.6. So should I keep washing my hands and being careful about elevator buttons, light switches, door knobs etc?

1.7. Where can I find more scientific information at a higher level about aerosol transmission?

2. General questions about aerosol transmission

2.1. What is aerosol transmission?

2.2 What is the size of infectious aerosols?

2.3 What factors control how many infectious aerosols are exhaled?

2.4. Where do aerosols of different sizes deposit in the human respiratory tract?

2.5. Some people say that “aerosols” vs. “droplet” transmission is a semantic discussion, and that both can infect by inhalation. Is that correct?

2.6. But many documents define aerosols as smaller than 5 μm and ballistic droplets as larger than that size. Is that incorrect?

2.7. How long does the SARS-CoV-2 remain infectious in aerosols?

2.8. Does temperature affect the survival of the virus in the air?

2.9. Does relative humidity (RH) affect transmission?

2.8. Is there an analogy for aerosol transmission?

2.9. Does that mean that smoking can help spread the virus?

2.10. Can pollution aerosols help spread the virus?

3. Protecting ourselves from aerosol transmission

3.1. At what distance from an infected person can I get infected?

3.2. Do the 1-2 m or 6 feet guidelines guarantee lack of infection indoors?

3.3. How long does one need to inhale infectious aerosol to be infected?

3.4. How long can the virus stay in the air indoors?

3.5. How can I protect myself from aerosol transmission indoors?

3.6. Is there a way to remember all the things I need to reduce or avoid?

3.7 Aren’t your recommendations the same as Japan’s 3 Cs?

3.8 Is there a way to understand the relative risk of different environments?

3.9 Is there a more quantitative way to investigate ways to reduce aerosol transmission?

4. Outdoors

4.1 Is there a risk of aerosol transmission outdoors?

4.2. Does UV light from the sun kill the virus?

4.3. Can I catch COVID-19 just by passing by someone indoors or outdoors?

4.4. Is it safe to eat outdoors at a restaurant?

4.5. Is it safe to go to the swimming pool, beach, or park?

5. Risk for specific situations

5.1. Is it safe to take a taxi cab or rideshare?

5.2. Is it safe to travel by airplane?

5.3 Are schools safe?

5.4 What do you suggest for dental offices?

5.5. What about elevators?

5.6. What about toilets?

5.7. My specific situation is not here, what can I do?

6. Music

6.1. Are singing or playing wind instruments indoors dangerous?

6.2. What kinds of instruments generate the most aerosol?

6.3. What are the current recommendations to reduce aerosol emissions for musicians?

6.4. What about playing music outdoors or using tents?

6.5. What research is ongoing about transmission for choirs and wind instruments?

6.6. What do you think of the masks being sold for singers?

7. Masks and other protections

7.1. Do masks work to reduce the aerosol spread of COVID-19?

7.2. What is the best type of mask?

7.3. How effective are different types of masks for the wearer and for others?

7.4. Do I need to wear a mask outside?

7.5. Is it OK to just wear the mask over my mouth and leave my nose out?

7.6. Is the fit of a mask important?

7.7. Where should I stand around someone with a poorly fitting mask?

7.8. Is it ok to remove my mask to talk?

7.9. But I have seen some video online that shows vaping aerosols going through a mask. Doesn’t this show that masks don’t work?

7.10. Are transparent masks safe?

7.11. Is there an easy way to assess my mask at home?

7.12. Do I need eye protection?

7.13. Are face shields and masks interchangeable?

7.14. Are plexiglass barriers helpful?

8. Ventilation

8.1. What do you mean by ventilation?

8.2. Are windows a good way to increase ventilation?

8.3. How are public buildings ventilated?

8.4. How can we quantify the ventilation rate in a space?

8.5 Can we use the CO2 level in a space to estimate whether ventilation is good or bad?

9. Filtering, and “air cleaning”

9.1. What filters should I use in my heating and/or air conditioning system?

9.2. Are portable air cleaners useful? Which types do you recommend?

9.3. What are HEPA portable air cleaners?

9.4. But if the virus is 0.1 μm, do HEPA / MERV filters (or masks) remove it from the air?

9.5. Is there a cheaper alternative to a HEPA air cleaner?

9.6. How do I select the right HEPA air cleaner? (or fan-filter cleaner)

9.7. Where should I place a HEPA air cleaner in a room?

9.8. How and when should filters be replaced?

9.9. Is germicidal ultraviolet light (UVC) effective as an air disinfection treatment for SARS-CoV-2?

9.10. Do you recommend portable air cleaners that are not based on filtration?

9.11. Do you recommend spraying disinfectants into indoor air to kill the virus?

9.12. Should we use humidifiers or dehumidifiers?

9.13. Should we keep indoor spaces hotter or colder to reduce transmission?


0. Questions about these FAQs

0.1. What is the goal of these FAQs?

The goal of these FAQs is to provide information to the general public in an efficient manner about how to prevent aerosol transmission of COVID-19, with the hope that this will allow more informed decision making by individuals or organizations. All of this information has been posted in Twitter and other forums, but can be difficult to find. Having multiple experts working together, and having the ability to update this information also improves its quality. These FAQs represent our best understanding at this time, and should always be similar or more stringent than information provided by CDC, WHO, and most regional & local health authorities. If your authority has a more stringent guideline than discussed here, follow that more stringent guideline.

0.2. Who has written these FAQs?

Scientists and engineers with many years of collective research experience related to indoor air quality, aerosol science, aerosol disease transmission, and engineered control systems for aerosols. Our contributors are active researchers investigating aerosol transmission of COVID-19 (see e.g. 1, 2, 3, and 4). Five of us were speakers at the recent Workshop on Airborne Transmission of COVID-19, organized by the US National Academies of Sciences, Engineering, and Medicine (the highest level scientific organization in the US). Three of us are members of a COVID-19 WHO expert group. Specifically, the writers of these FAQs include Professors :

* Prof. Linsey Marr (Virginia Tech, Fellow ISIAQ)

* Prof. Shelly Miller (CU Boulder, Fellow ISIAQ)

* Prof. Kimberly Prather (UC San Diego, Fellow AAAS & AGU, NAE & NAS, CAICE Director)

* Prof. Charles Haas (Drexel University, Fellow AAM & SRA)

* Prof. William Bahnfleth (Penn State, Fellow ASHRAE, ASME & ISIAQ, Chair of ASHRAE Epidemic Task Force)

* Prof. Richard Corsi (Portland State, President ISIAQ Fellows)

* Prof. Julian Tang (Univ. of Leicester & UK National Health Svce, Clinical/Academic Virologist/Physician, Fellow RCP-Virology)

* Prof. Hartmut Herrmann (Dept. Head, Leibniz-Institute for Tropospheric Research (TROPOS), University of Leipzig; Head Joint Working Party ‘PM’ of GDCh, KRDL and ProcessNet).

* Prof. Krystal Pollitt (School of Public Health, Yale University, Chair of Health-Effects Working Group AAAR)

* Prof. Jose-Luis Jimenez (CU Boulder, Highly Cited Researcher (h-index = 121), Fellow AAAR & AGU).

Several additional scientists are also working with us to contribute to this document. If other experts are interested in contributing to these FAQs or other related efforts, please contact Jose.

We think that unfortunately WHO and CDC are being too slow to accept aerosol transmission, hence the need for these FAQs directly from the scientists.

0.3. I found a mistake, or would like something to be added or clarified, can you do that?

We will update these FAQs in response to feedback, to fix any mistakes, or to expand them in response to questions (as time allows). Please complete the form at this link with any updates, errors, suggestions etc. Please do not send questions via email or Twitter, as it is too cumbersome to try to keep track of those.

0.4. Are these FAQs available in other languages?

At present we are making or planning a lot of updates, in response to a lot of questions and requests. But Google can translate it into many languages automatically. See

* Traduccion al espanol

* Traduction au français

* German translation

* For other languages, go to this page and change the language at the top

0.5. Can I use the information here in other publications etc.?

You are welcome to use any of this as you see fit. There is no need to contact us for permission. We only ask that you give the link http://tinyurl.com/faqs-aerosol as the source of the information. Please include the date and version number gi

FAQs on Protecting Yourself from Aerosol Transmission
Tags Coronavirus, Guide, Masks, Healthcare, Coronavirus masks, Airborne precautions, N95
Type Google Doc
Published 27/10/2020, 15:46:48


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