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I was curious how indoor CO2 levels change from people breathing, so I did a quick calculation. A small room is 4m x 4m x 2.5m. That would contain 40m^3 of air
by ggreer 11y ago
I was curious how indoor CO2 levels change from people breathing, so I did a quick calculation. A small room is 4m x 4m x 2.5m. That would contain 40m^3 of air or 40000 liters, 8000 of which is oxygen. From what I can gather, a normal person working will use 30 liters of oxygen per hour.[1] If the room contained one person and was completely sealed for 8 hours, it would end with 7760L of oxygen, 192L of CO2, and some water vapor. Around 0.5% of the atmosphere in the room would be CO2. While at the occupational limit, that's still enough to cause drowsiness and mental fatigue.[2]
It's surprising how little CO2 is required to disrupt cognition. Still, even getting to those levels would take an extremely stuffy office. I'm not convinced this is a issue in most workplaces.
1. http://www.molecularproducts.com/pdf/technical-library/A%20Guide%20to%20Breathing%20Rates%20in%20Confined%20Environments%20Technical%20Article.pdf http://www.molecularproducts.com/pdf/technical-library/A%20G...
2. https://en.wikipedia.org/wiki/Carbon_dioxide#Toxicity https://en.wikipedia.org/wiki/Carbon_dioxide#Toxicity
- roel_v 11y agoI'm not sure if we're arguing the same point and if we agree or not, but e.g. http://piers.org/piersonline/download.php?file=MDkwMjIwMTQ0NjQwfFZvbDVObzdQYWdlNjM3dG82NDAucGRm http://piers.org/piersonline/download.php?file=MDkwMjIwMTQ0N... ('Ventilation Efficiency and Carbon Dioxide (CO2) Concentration', Progress in Electromagnetics Research Symposium vol 5 no 7, 2009) seems to suggest that even in workplaces with air conditioning (albeit old airco and densely populated rooms), CO2 concentrations can reach higher-than-recommended levels in everyday usage. Any modern residential building requires mechanical ventilation to keep CO2 levels in check. CO2 levels, in real-world usage, also don't rise linearly - opening the windows for 30 minutes in the morning is not ventilation. IIRC (although I don't have a reference at hand) rooms reach 70% of their pre-window-opening levels within less than an hour of closing them. (maybe, although again I don't recall details, because of CO2 in other rooms, or maybe it gets 'cached' in materials (sound unlikely though... guess I'm giving away my lack of chemistry knowledge here), or other reasons?) Point being - in building design/architecture it's assumed knowledge that CO2 does rise to higher-than-recommended levels in modern (i.e., low air leakage) buildings without mechanical ventilation.
- andor 11y agoFrom the Wikipedia article: "Another study of humans exposed in 2.5 hour sessions demonstrated significant effects on cognitive abilities at concentrations as low as 0.1% (1000ppm) CO2 likely due to CO2 induced increases in cerebral blood flow." You can easily reach .1% in a normal office. Therefore, office-environmentally conscious people install CO2 sensors ;-) Here's an example: https://metrics.librato.com/share/dashboards/l7pd2aia?duration=608400 https://metrics.librato.com/share/dashboards/l7pd2aia?durati...