FAQs on Protecting Yourself from COVID-19 Aerosol Transmission | Table of Contents

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 Are all infected people equally contagious?
  • 1.5. So should I keep washing my hands and being careful about elevator buttons, light switches, door knobs etc?
  • 1.6 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 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. Are portable air cleaners useful? Which types do you recommend?
  • 9.2. What are HEPA portable air cleaners?
  • 9.3. But if the virus is 0.1 μm, do HEPA / MERV filters (or masks) remove it from the air?
  • 9.4. Is there a cheaper alternative to a HEPA air cleaner?
  • 9.5. How do I select the right HEPA air cleaner? (or fan-filter cleaner)
  • 9.6. Where should I place a HEPA air cleaner in a room?
  • 9.7. How and when should filters be replaced?
  • 9.8. Is germicidal ultraviolet light (UVC) effective as an air disinfection treatment for SARS-CoV-2?
  • 9.9. Do you recommend portable air cleaners that are not based on filtration?
  • 9.10. Do you recommend spraying disinfectants into indoor air to kill the virus?
  • 9.11. Should we use humidifiers or dehumidifiers?
  • 9.12. Should we keep indoor spaces hotter or colder to reduce transmission?

See our other articles or take a look at our research paper summaries.

Read the Reflow Labs Airsafe White Paper

Published with authorization to use copy "as you see fit" with attribution as specified. https://tinyurl.com/FAQ-aerosols, Version: 1.60, 14-Sep-2020

Learn more about our board of reviewers.


Get In Touch

Email sales@reflowlabs.com or leave a message here to learn more about our products (>25,000 sqf at this time only, please).

Are you a small business or individual? Join our mailing list today and we'll let you know when our webstor for direct sales are live.


© Reflow Labs, LLC. All rights reserved.