Thread by @RichardBarrow

😷 I’ve been invited to join an international campaign to research the potential dangers in shops and indoor venues. In this mega THREAD, I will be using a CO2 meter to measure the Covid-19 risks that we all face #Thailand #COVIDisAirborne #โควิดแพร่ทางอากาศ #CovidCO2 #โควิดco2

Measuring the virus in the air is not easy. But CO2 meters recognize exhaled air inside rooms and so is a good proxy for the aerosols that carry the virus. If it’s 1,500 ppm that means 1.5% of the air has been in someone else’s lungs. Today I tested CO2 in three shops.

https://twitter.com/thaiairquality/status/1431504724482609157

The first lesson I learned today is that you should be very careful in a vehicle. Anything over 800 ppm is risky if you’re not alone. With recirculating turned on it was 1885 ppm. In a taxi, ask the driver to turn it off or open a window or two #CovidCO2 #โควิดco2 #WearAMask

On my way home I turned off recirculating. I normally have it on all the time as I’m worried about exhaust fumes entering the car in Bangkok’s notorious traffic jams. Not so. With windows closed and air-con on, it was only 633 ppm #CovidCO2 #โควิดco2 #Thailand

My first stop was Villa Market on Rama III road. Outside CO2 was 590 ppm but inside the supermarket it was a high 1442 ppm. Make sure you #WearAMask. I really hope they have a good filtration system. If not, you don’t want to stay too long #COVIDisAirborne #CovidCO2 #Thailand

My next stop was Lotus on Rama III road. This supermarket is much bigger than Villa but it was very crowded and so I was concerned. However, the CO2 reading stayed below the recommended 800 ppm throughout the store #COVIDisAirborne #โควิดแพร่ทางอากาศ #CovidCO2 #โควิดco2 #Thailand

On my way home I stopped at a 7-11 convenience store. The CO2 reading was below the 800 ppm recommended by the Thai Ministry of Public Health. Maybe because the doors open often or less people than a supermarket #COVIDisAirborne #โควิดแพร่ทางอากาศ #CovidCO2 #โควิดco2 #Thailand

This is the graph of my trip today. Any indoor place that has a CO2 reading of more than 800 ppm is a potential risk for Covid-19. All shops should be well ventilated and have good filters. Tomorrow I will visit more places #COVIDisAirborne #โควิดแพร่ทางอากาศ #CovidCO2 #โควิดco2

Now that the Ministry of Public Health has suggested the use of CO2 meters in indoor venues to check for good ventilation, I hope cinemas in #Thailand will do like this Japanese one 👇 to show patrons CO2 levels in each screen. They look well ventilated #COVIDisAirborne #CovidCO2

https://twitter.com/NOGjp/status/1418146334612221953

Now that #Thailand is preparing to re-open some indoor venues, I’m using a #CovidCO2 meter to see how well ventilated places are. It’s very difficult to measure for the presence of #COVID19, but CO2 is a good proxy. But, it’s not perfect as I’ll talk about later #COVIDisAirborne

I was only in this taxi for 25 minutes but I was so glad I was wearing a tight-fitting KN95 mask. This taxi’s CO2 reading was 2764 ppm. He told me he had been driving for 9 hours. At this level, 5% of the air was exhaled by someone else #COVIDisAirborne #CovidCO2 #Thailand

The CO2 reading roadside before I got in the taxi was 509 ppm but it quickly increased because he had recirculating on. Virus-laden aerosols can stay in the air for hours. I told him he should turn it off & open the windows between passengers #Thailand #COVIDisAirborne #CovidCO2

Any CO2 reading below 800 is relatively safe. While I was riding the BTS Skytrain this evening the highest it went was 776 ppm. It was probably well ventilated due to the doors opening often. If the air is filtered as well then all is good #COVIDisAirborne #CovidCO2 #โควิดco2

In between each #CovidCO2 test I’m sitting outside for about 5-10 minutes so you can clearly see each mode of transport when I post the graph of this trip. This is Sala Daeng intersection. Surprisingly it was only 500 ppm #โควิดco2 #COVIDisAirborne #โควิดแพร่ทางอากาศ #Thailand

Not surprisingly, the MRT Subway had higher CO2 levels than the Skytrain. It started off good at around 688 ppm but as more and more people came onboard it peaked at 956 ppm. At this level, 1.5% of the air has been exhaled by someone else #COVIDisAirborne #CovidCO2 #Thailand

I got off the crowded subway train and board another one going the opposite way. This one was nearly empty and the CO2 levels were only 644 ppm. Far more acceptable. Avoid crowded trains during a pandemic #COVIDisAirborne #โควิดแพร่ทางอากาศ #CovidCO2 #โควิดco2

I’m really surprised that carbon dioxide levels are so low at intersections in #Bangkok. This is by BTS Asoka station. I know the roads are not as busy, as many people are working from home, but still, 466 ppm seems very low #COVIDisAirborne #โควิดแพร่ทางอากาศ #CovidCO2 #โควิดco2

My trip home on the BTS Skytrain showed a higher CO2 level. It peaked at 969 ppm when I reached On Nut station. Probably because it was so crowded with commuters heading home. But also because the doors were never opened for long #COVIDisAirborne #CovidCO2 #โควิดco2 #Thailand

My taxi ride just now had extremely high CO2 levels at 3031 ppm. That means 7% of the air has been in someone else’s lungs. Hopefully other passengers didn’t have Covid. I told him that he needs to turn off recirculating & open the windows between rides #COVIDisAirborne #CovidCO2

Here is the graph of my trip to #Bangkok and back. The Thai Ministry of Health says any CO2 reading above 800 ppm in an enclosed space could put you your health at risk because #COVIDisAirborne. Don’t ride crowded trains and make sure taxis are not recirculating air #CovidCO2

If you want to read more about airborne transmission of respiratory viruses, then check out this fascinating article 👇 Check out these hashtags too. Thanks for following along on this mega thread.

#COVIDisAirborne #โควิดแพร่ทางอากาศ #CovidCO2 #โควิดco2

https://twitter.com/zeynep/status/1431248145497927687

I’m working with @zerocovidthai to help spread the message that #COVIDisAirborne and of the dangers in unventilated rooms. They sent out CO2 meters to people in SE Asia including myself. Read their THREAD below about using these sensors as an infection risk proxy #CovidCO2 👇

https://twitter.com/zerocovidthai/status/1432619566467731460

When you visit a shop, check they have proper ventilation and air filtration. Some places now have CO2 monitoring so you can check to see if targets are met. Read the science paper below 👇 to see how a CO2 monitor can be used as an infection risk proxy #COVIDisAirborne #CovidCO2

https://twitter.com/thaiairquality/status/1433956005717495808

When I was at Villa Market in the late afternoon last weekend to do my weekly shopping, the CO2 levels were a high 1442 ppm which suggested bad ventilation. Today I went early morning to see the difference. As you can see, at 862 ppm it’s a safer level #CovidCO2 #COVIDisAirborne

As #COVIDisAirborne, it’s a good idea to visit malls and supermarkets when they first open or less crowded. Use Google Maps to get an idea of which days and times are the least busy. Also don’t forget to take a good fitting KN95/N95 mask #CovidCO2 #wearamask #Thailand

On my way home, I stopped at Foodland on Srinakarin road to buy a few supplies. While I was there I checked out the CO2 reading and as you can see, at a low 700 ppm it means the supermarket is well ventilated despite being busy with shoppers #COVIDisAirborne #CovidCO2 #Thailand