Read on Twitter
1/ Using CO2 indoors to monitor infection risk
- Very good idea
- Limitation: one limit (e.g. 800 ppm) does not work for all situations.
- Preprint from: @ZheP_AtmChem & I: https://www.medrxiv.org/content/10.1101/2020.09.09.20191676v1
- Key result: need to estimate a CO2 limit for each situation
#covidco2
- Very good idea
- Limitation: one limit (e.g. 800 ppm) does not work for all situations.
- Preprint from: @ZheP_AtmChem & I: https://www.medrxiv.org/content/10.1101/2020.09.09.20191676v1
- Key result: need to estimate a CO2 limit for each situation
#covidco2
2/ Why does it work?
- Because infected humans exhale CO2 and SARS-CoV-2 as they breathe, talk etc.
- Both CO2 and virus removed by ventilation with outdoor air
#covidco2
- Because infected humans exhale CO2 and SARS-CoV-2 as they breathe, talk etc.
- Both CO2 and virus removed by ventilation with outdoor air
#covidco2
3/ Why does it depend on the situation?
Most importantly because:
- Talking / singing / shouting... enhance virus emission FAR more than CO2
- Risk depends strongly on how many infected ppl in a region
- Masks, filters, HEPA cleaners remove viruses, not CO2
#covidco2
Most importantly because:
- Talking / singing / shouting... enhance virus emission FAR more than CO2
- Risk depends strongly on how many infected ppl in a region
- Masks, filters, HEPA cleaners remove viruses, not CO2
#covidco2
4/ Why does it depend on the situation?
Other reasons:
- Virus decays in ~1 h in the air, CO2 does not
- Virus-containing particles settle to ground in ~few h (possibly faster, depends on size distribution), CO2 does not
#covidco2
Other reasons:
- Virus decays in ~1 h in the air, CO2 does not
- Virus-containing particles settle to ground in ~few h (possibly faster, depends on size distribution), CO2 does not
#covidco2
5/ Results: CO2 threshold for a given infection risk can vary to a factor of 100
- Top: variations of a classroom
- Middle: variation with activity
- Bottom: other cases
#covidco2
- Top: variations of a classroom
- Middle: variation with activity
- Bottom: other cases
#covidco2
6/ What is the CO2 threshold in your situation?
- Use http://tinyurl.com/covid-estimator to calculate
- Also need to factor in what risk of infection is deemed acceptable. In the paper we chose a chance of 1 in 10000 (0.01%) for doing an activity once.
#covidco2
- Use http://tinyurl.com/covid-estimator to calculate
- Also need to factor in what risk of infection is deemed acceptable. In the paper we chose a chance of 1 in 10000 (0.01%) for doing an activity once.
#covidco2
7/ As always feedback is appreciated.
Quick comments in Twitter are ok, email preferred for more detailed comments.
Will add calculator of CO2 for a given situation to online estimator
Ppl are welcome to build upon this work if it's useful. A lot more that can be done.
Quick comments in Twitter are ok, email preferred for more detailed comments.
Will add calculator of CO2 for a given situation to online estimator
Ppl are welcome to build upon this work if it's useful. A lot more that can be done.
8/ This is a diagram of the processes that affect SARS-CoV-2 in aerosols and CO2 in indoor environments
#covidco2
(Forgot to paste it above)
#covidco2
(Forgot to paste it above)
