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Calculate the Amount of Shared Air in an Indoor Space using CO2 Levels
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Created by:Dr. Jeff Gilchrist
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Last updated:February 26, 2021
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Rebreathed fraction of air (f) is how much air someone inhales that came out of other people in an indoor space.
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For example if f = 0.05 that means every breath you take contains 5% of the collective breath of others.
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Summary of rebreathed fraction calculations:
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Summary of inhaled liters/hour calculations:
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For more details on these calculations please see paper:
https://doi.org/10.1034/j.1600-0668.2003.00189.x
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Inspired by David Elfstrom's table:
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For an index of my COVID-19 related articles see:
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For my daily COVID-19 related statistics and graphs:
http://gilchrist.ca/jeff/COVID-19/
http://gilchrist.ca/jeff/COVID-19/vaccine.html
http://gilchrist.ca/jeff/COVID-19/Ottawa.html
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Rebreathed Fraction Formula:f = (Cavg - Cout) / Cbreath
Cavg = average indoor, Cout = average outdoor, Cbreath = exhaled CO2 concentrations
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Inhaled Liters/Hour Formula:ILday / 24 * f
ILday = typical air inhaled liters a day, f = rebreathed fraction (see above)
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Pandemic CO2 Level Traffic Light Guidelines:< 700 ppm700 - 800 ppm> 800 ppmSee:
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Your Indoor CO2 in ppm (Cavg):3152
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Outdoor CO2 in ppm (Cout):416See:
https://keelingcurve.ucsd.edu/
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Exhaled CO2 in ppm (Cbreath):38000See:
(generally 38000 ppm for rest and active)
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Inhaled Liters/Day of Air (ILday):10000See:
(generally 10,000 liters air inhaled per day at rest/office work)
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Rebreathed Fraction of Air (f):0.07200000000
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Shared Air:7.20%
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Inhaled Liters/Hour of Other's Breath:30.0
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Indoor CO2 Levels (PPM)Shared Air (%)Inhaled Liters/Hour
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4500.09%0.4
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5000.22%0.9
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6000.48%2.0
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7000.75%3.1
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8001.01%4.2
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9001.27%5.3
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10001.54%6.4
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15002.85%11.9
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20004.17%17.4
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25005.48%22.9
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30006.80%28.3
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35008.12%33.8
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40009.43%39.3
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450010.75%44.8
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500012.06%50.3
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Note: Feel free to make a copy of this spreadsheet and change your indoor CO2, the outdoor and exhaled CO2, inhaled liters/day of air,
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and list of indoor CO2 concentrations for your area and calculate what you are interested in knowing.
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You can do this by selecting "File -> Make a copy" within Google Sheets which will let you edit the values.
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