John Wenger Profile picture
Mar 7, 2022 9 tweets 4 min read Read on X
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
Flight 3 (Embraer 190 aircraft, 95% full):

Lower CO2 levels while boarding in this case, but still peaking at 2000 ppm mid-flight and 2500 ppm while disembarking.

4/ Image
Flight 4 (Embraer 190 aircraft, 95% full):

Same aircraft as Flight 1 and very similar profile, except for disembarking period where the CO2 levels did not rise sharply because (for some reason) the air supply remained on.

5/ Image
During the flight, air is refreshed and passed through HEPA filters, so the number of airborne respiratory particles (and COVID transmission risk) is greatly reduced, even if CO2 is 1800-2000 ppm.

6/

Highest risk of COVID transmission is during boarding & disembarking because:
1. Respiratory rates are higher when people are moving than when sitting down during the flight.
2. Air circulation and filtration are generally not operating to the same extent as mid-flight.

7/
These CO2 levels are within the normal range that I have come across.
Thankfully, they were a lot lower than this😲👇

8/

But it would be great if airlines could increase fresh air delivery rates further during the flight (CO2 levels of 2000 ppm for several hours is not great!) and especially during boarding/disembarking.

End

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More from @johnwenger9

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
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
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
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
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
May 16, 2021
#covidco2
Hairdressers and barbers were allowed to open in Ireland last week, so I lent a CO2 monitor to my friend Nora, who runs a hairdressing salon in Cork city.

The monitor (circled in red) was placed in the middle, unused station, 1-2 m from the chairs.

1/
I gave Nora some simple advice - keep a window open and increase ventilation if the CO2 level rises above 800 ppm.

Results from Day 1 show levels rise to around 800 ppm even with window open.

When Nora noticed this she opened the door slightly and the CO2 dropped rapidly.

2/
Results from Day 2 are very similar.

The window was always open, but CO2 levels only drop when the door is also opened.

This shows the importance of cross ventilation for clearing the air.

Open doors and windows that are opposite to each other to ensure a flow of air.

3/
Read 6 tweets

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