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John Wenger Profile picture
@johnwenger9
Sep 21, 2020 • 5 tweets • 2 min read • Read on X
Big development in USA as the Center for Disease Prevention and Control acknowledges that exhaled aerosols play a major and possibly dominant role in transmission of coronavirus.
latimes.com/world-nation/s…
Side by side comparison of new and old guidance from CDC...
Congratulations to the aerosol scientists and indoor air quality experts in USA who have worked tirelessly for agency recognition of aerosol transmission. Now we need the European CDC and WHO to move in the same direction.
Aerosols containing the virus can travel more than 2 metres and remain suspended in air for several hours. This highlights the importance of mask wearing in all shared indoor spaces, as well as good ventilation to remove the virus from the air. Read this time.com/5883081/covid-…
Check out this comprehensive guide on aerosol transmission docs.google.com/document/d/e/2…

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More from @johnwenger9

John Wenger Profile picture
Feb 21, 2023
I put a CO2 monitor in the mesh pocket of my backpack during a short trip to #London last week.

Thread on the observations:

Note the traffic light colour scale:
Green = CO2 below 1000 ppm
Amber = C02 between 1000-1400 ppm
Red = CO2 over 1400 ppm
The highest readings were recorded during the Cork-Stansted return flights.
Typical "Batman Ears" profile obtained for both flights due to lack of ventilation during boarding & disembarking.
@Ryanair - a CO2 reading of 4000 ppm is very unhealthy. Turn the ventilation on earlier!
Ventilation gradually improved on the @Stansted_Exp train once we got going and CO2 stayed in the green on the first underground trip.

But we quickly hit the red on the next @TfL underground trip - a crowded Northern line train to Camden Town.
Read 10 tweets
John Wenger Profile picture
Nov 26, 2022
New publication shows that the recommended minimum ventilation rate of 6 air changes per hour (ACH) for a 6 bed ward commonly found in hospitals across Ireland & UK could only be achieved by combining natural ventilation with HEPA filtration.

1/
 journalofhospitalinfection.com/article/S0195-…
Values for effective ACH were obtained from the measured decay rates of respirable particles (< PM2.5) under different conditions.
Fully open windows alone delivered 4.5 ACH, while the HEPA air filter unit (AFU) alone delivered 4.8 ACH.
The combination delivered 11.2 ACH.

2/ Image
There are thousands of wards like this across Ireland & UK that rely solely on natural ventilation.
It is highly unlikely the windows will be fully open during winter months, so it is clear that HEPA filters are needed to deliver the effective ACH required in these wards.

3/
Read 6 tweets
John Wenger Profile picture
Aug 28, 2022
Schools are back and there are many concerned parents and teachers asking what measures are in place to reduce the spread of COVID-19.

Short thread. #edchatie
The mask mandate was removed at the end of February 2022, but schools were advised to continue using infection prevention and control measures, such as ventilation.

gov.ie/en/press-relea…
As far as I know this advice has not changed, so windows should be open, CO2 monitors in use and HEPA filters turned on.

However, with the more laissez-faire approach to COVID-19 adopted across society over the last 6 months, schools could do with some clarification.
Read 8 tweets
John Wenger Profile picture
Mar 7, 2022
Thread on the CO2 readings that I took during my four short flights with @KLM @KLM_EIR last week.
Remember, CO2 at 800 ppm means that 1% of the air you breathe in has been breathed out by others.
At 1200 ppm the rebreathed fraction is 2%.
At 2400 ppm it is 5%.
#CovidCO2
1/
Flight 1 (Embraer 175 aircraft, 95% full):
~500 ppm in @CorkAirport
Shoots up to 2400 ppm while boarding, drops when air circulation kicks in.
Settles around 1900 ppm mid flight. Rises to 2500 ppm when disembarking.
RH ~30% on plane.

2/ Image
Flight 2 (Boeing 737-700, 60-70% full).
Similar profile but levels much lower
on this bigger aircraft.
The air felt fresher and CO2 levels reflected that.

3/ Image
Read 9 tweets
John Wenger Profile picture
Sep 12, 2021
For the last 6 weeks I have been working with the Castle Hotel in Macroom @castleHmacroom on a CO2 monitoring & ventilation project.

Here is a (long!) thread on the very interesting results we obtained.
#covidco2
1/
The Castle Hotel is a traditional family-run hotel. The building is old - last major refurbishment was in the early 2000s. Mechanical and natural ventilation are available in most areas. I was pleased to see that front doors are wide open throughout the day!
2/
The first step was to get the maintenance staff to complete the @HSA ventilation checklist.
3/
 hsa.ie/eng/topics/cov…
Read 22 tweets
John Wenger Profile picture
May 27, 2021
Hooray!

The Department of Education @Education_Ire today published updated guidance on ventilation in schools.

It includes further practical advice on natural ventilation, the use of CO2 monitors (some good news for schools here!) and air cleaners.

1/
gov.ie/en/publication…
Also, very pleased to report that the guidance incorporates a lot of the advice provided by The Expert Group on ventilation and COVID-19 which includes @Orla_Hegarty @IAQjones @MoyneFlu @MarieCoggins1 @DrInaKelly1, myself and others.

2/

gov.ie/en/publication….
The guidance contains some excellent practical tips on letting fresh air into buildings, such as cross ventilation for optimum airflow.

This advice is not only for schools - it could be used to improve the fresh air supply in all buildings that rely on natural ventilation.

3/
Read 5 tweets

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