5 ms·

We do indoor air quality monitoring and see very different results across buildings. The biggest differentiator is if the building has mechanical ventilation a

We do indoor air quality monitoring and see very different results across buildings. The biggest differentiator is if the building has mechanical ventilation and to what extent this mechanical ventilation uses fresh air vs internal circulation. In unventilated crowded spaces like e.g. classrooms, we regularly see CO2 exceeding 3500 ppm. [1] However in classrooms with a well designed ventilation system you can keep the CO2 < 1000ppm during the whole school day. What the author did in his hotel room to turn on the fan or play around with the A/C settings is a good idea but many hotels Hvac systems do not draw in sufficient fresh air and you will see high CO2 developments. [1] https://www.airgradient.com/open-airgradient/blog/we-measured-the-co2-level-in-a-classrooms-this-is-what-we-found-out/ https://www.airgradient.com/open-airgradient/blog/we-measure...

icelancer 4y ago
3500ppm? That would imply an average CO2 level well above 1000ppm. No wonder why it's impossible to stay focused in lecture halls...
- MichaelZuo 4y ago
  Yeah, that really makes me rethink my entire education experience...
  - JohnBooty 4y ago
    ...you could always distract yourself by thinking about all of the political and military decisions that have been made throughout history, affecting millions and billions of human lives, in stuffy cramped rooms with excessively high CO2 levels. ...wait, that's not helping?
    - MichaelZuo 4y ago
      The utopia of adequate ventilation.
    - p1esk 4y ago
      A cynical view - with better CO2 levels the outcome of those political/military decisions could be worse.
Reason077 4y ago
Perhaps CO2 sensors should be part of the standard HVAC sensor suite in big buildings? That is, along with measuring temperature, the sensors in each room should also measure CO2 levels. If CO2 is rising, fans can be turned on/turned up to bring more fresh air into the room.
- ArchitectAnon 4y ago
  They are legally required in the primary bedroom of all new build houses in Scotland, possibly also in England and Wales.
  - Reason077 4y ago
    Huh? Really? Are you thinking of Carbon Monoxide detectors, perhaps? Sometimes these are incorrectly called "CO2 detectors".
    - sampo 4y ago
      Appears to be true: > CO2 monitoring equipment should be provided in the apartment expected to be the main or principal bedroom in a dwelling where infiltrating air rates are less than 15m3/hr/m2 @ 50 Pa. https://www.gov.scot/publications/building-standards-2017-domestic/3-environment/314-ventilation/ https://www.gov.scot/publications/building-standards-2017-do... Well done, Scotland.
      - pifm_guy 4y ago
        Monitoring equipment alone isn't really sufficient, unless it is hooked up to a fan or ventilation equipment to maintain a suitable level, and an alarm to alert if that level can't be maintained. If the law requires just monitoring equipment, then you know that in a utility cabinet somewhere will be a screen with the data on, that nobody ever looks at, and might as well not be there.
    - deleted 4y ago
      [deleted]
mistr0 4y ago
I teach in a UK secondary school; the building with my classroom in was built in the 1960s, as many of them are. Ventilation is poor and after a 60-minute lesson with 25-30 students (age ~15) CO2 will be at 2000-2500 ppm. If there are back-to-back lessons it'll be 3000-3500. I can open some doors, but they lead to connected classrooms so this is only practical if those rooms are not in use. Retro-fitting an AC system is likely possible, but expensive.
- Arbortheus 4y ago
  Air quality should be a bigger consideration in schools, I bet students will be more attentative and able to focus better without high CO2 levels. We should create the conditions to allow them to succeed.
- ahaucnx 4y ago
  You might be interested to join the SAMHE project in the UK [1] (that we are part of). It gives free air quality monitors to secondary schools for a large scientific study. [1] https://www.samhe.org.uk/ https://www.samhe.org.uk/
rsync 4y ago
"However in classrooms with a well designed ventilation system you can keep the CO2 < 1000ppm during the whole school day." Where does "opening the windows" fit in a scale of "well designed ventilation systems" ? I'm not being flip, or snarky - I'm serious. I don't think it's terribly sophisticated or haughty to consider lack of opening windows to be a poverty. Hotel rooms, hospital rooms, classrooms ... whatever ... windows that cannot be opened is a poverty.
- kragen 4y ago
  it varies, but usually opening the windows is plenty of ventilation unless it's not an option (e.g., because it's too hot or too cold outside) it's much more common to wish for bigger windows because you're hot than because you're falling asleep by virtue of stuffing 30 people into a single room you force them to compromise on environmental conditions; whoever's out in the tails of the distribution or has low social status is going to get screwed over because the resulting compromise will favor average people and people of high social status that's just how compromises work, people struggle to promote their conflicting interests, so popular people and people with popular interests win but typically you can still find a compromise that's pretty okay for 90+% of people (1000 ppmv - 420 ppmv) co₂ = 580 ppmv co₂ r 20° / 1 atm = 24 ℓ/mol 1 kg co₂ / day / 人 = 11.6 mg co₂ / s / 人 30 人 · 11.6 mg co₂ / s / 人 / (44 g co₂/mol co₂) = 7.9 mmol co₂ / s (a classroom) 7.9 mmol co₂ / s · 24 ℓ/mol = 0.19 ℓ co₂ / s 0.19 ℓ co₂ / s / 580 ppmv co₂ = 330 ℓ / s (of air) in medieval units that's about 700 'cfm' if the classroom has 10 m² of open windows you're fine, even an undetectable draft of 0.03 m/s is sufficient, but if it has 1 m² you need a barely detectable breeze of 0.3 m/s, if it has 0.1 m² you need a pretty noticeable breeze of 3 m/s ('light breeze' on the beaufort scale), and if it has a little 100-mm-square register you need 30 m/s which is a 'violent storm' on the beaufort scale (above 'whole gale') at 'fresh breeze' (8–11 m/s) you need 300–400 cm² of window well designed ventilation systems can provide this kind of airflow while controlling the temperature and humidity but they are at a big disadvantage because 300–400 cm² of window is a lot smaller than 300–400 cm² of duct sometimes that's not what matters most tho
sireat 4y ago
I was surprised how well a large modern building ventilates CO2. We had some employees complain about feeling "stuffy" when air conditioning was turned off(due to budget constraints). So maintenance brought their own CO2 meter and I brought my trusty Aranet4. Both our readings were around 650 in a medium sized office with 4 people. Apparently the raise of temperature from 22C to 26C was enough to trigger internal "stuffiness". PS By comparison my bedroom regularly reaches 3000 in the mornings if no windows are left open.

icelancer 4y ago

3500ppm? That would imply an average CO2 level well above 1000ppm. No wonder why it's impossible to stay focused in lecture halls...

MichaelZuo 4y ago
Yeah, that really makes me rethink my entire education experience...
- JohnBooty 4y ago
  ...you could always distract yourself by thinking about all of the political and military decisions that have been made throughout history, affecting millions and billions of human lives, in stuffy cramped rooms with excessively high CO2 levels. ...wait, that's not helping?
  - MichaelZuo 4y ago
    The utopia of adequate ventilation.
  - p1esk 4y ago
    A cynical view - with better CO2 levels the outcome of those political/military decisions could be worse.

Reason077 4y ago

Perhaps CO2 sensors should be part of the standard HVAC sensor suite in big buildings? That is, along with measuring temperature, the sensors in each room should also measure CO2 levels. If CO2 is rising, fans can be turned on/turned up to bring more fresh air into the room.

ArchitectAnon 4y ago
They are legally required in the primary bedroom of all new build houses in Scotland, possibly also in England and Wales.
- Reason077 4y ago
  Huh? Really? Are you thinking of Carbon Monoxide detectors, perhaps? Sometimes these are incorrectly called "CO2 detectors".
  - sampo 4y ago
    Appears to be true: > CO2 monitoring equipment should be provided in the apartment expected to be the main or principal bedroom in a dwelling where infiltrating air rates are less than 15m3/hr/m2 @ 50 Pa. https://www.gov.scot/publications/building-standards-2017-domestic/3-environment/314-ventilation/ https://www.gov.scot/publications/building-standards-2017-do... Well done, Scotland.
    - pifm_guy 4y ago
      Monitoring equipment alone isn't really sufficient, unless it is hooked up to a fan or ventilation equipment to maintain a suitable level, and an alarm to alert if that level can't be maintained. If the law requires just monitoring equipment, then you know that in a utility cabinet somewhere will be a screen with the data on, that nobody ever looks at, and might as well not be there.
  - deleted 4y ago
    [deleted]

mistr0 4y ago

I teach in a UK secondary school; the building with my classroom in was built in the 1960s, as many of them are. Ventilation is poor and after a 60-minute lesson with 25-30 students (age ~15) CO2 will be at 2000-2500 ppm. If there are back-to-back lessons it'll be 3000-3500. I can open some doors, but they lead to connected classrooms so this is only practical if those rooms are not in use. Retro-fitting an AC system is likely possible, but expensive.

Arbortheus 4y ago
Air quality should be a bigger consideration in schools, I bet students will be more attentative and able to focus better without high CO2 levels. We should create the conditions to allow them to succeed.
ahaucnx 4y ago
You might be interested to join the SAMHE project in the UK [1] (that we are part of). It gives free air quality monitors to secondary schools for a large scientific study. [1] https://www.samhe.org.uk/ https://www.samhe.org.uk/

rsync 4y ago

"However in classrooms with a well designed ventilation system you can keep the CO2 < 1000ppm during the whole school day." Where does "opening the windows" fit in a scale of "well designed ventilation systems" ? I'm not being flip, or snarky - I'm serious. I don't think it's terribly sophisticated or haughty to consider lack of opening windows to be a poverty. Hotel rooms, hospital rooms, classrooms ... whatever ... windows that cannot be opened is a poverty.

kragen 4y ago
it varies, but usually opening the windows is plenty of ventilation unless it's not an option (e.g., because it's too hot or too cold outside) it's much more common to wish for bigger windows because you're hot than because you're falling asleep by virtue of stuffing 30 people into a single room you force them to compromise on environmental conditions; whoever's out in the tails of the distribution or has low social status is going to get screwed over because the resulting compromise will favor average people and people of high social status that's just how compromises work, people struggle to promote their conflicting interests, so popular people and people with popular interests win but typically you can still find a compromise that's pretty okay for 90+% of people (1000 ppmv - 420 ppmv) co₂ = 580 ppmv co₂ r 20° / 1 atm = 24 ℓ/mol 1 kg co₂ / day / 人 = 11.6 mg co₂ / s / 人 30 人 · 11.6 mg co₂ / s / 人 / (44 g co₂/mol co₂) = 7.9 mmol co₂ / s (a classroom) 7.9 mmol co₂ / s · 24 ℓ/mol = 0.19 ℓ co₂ / s 0.19 ℓ co₂ / s / 580 ppmv co₂ = 330 ℓ / s (of air) in medieval units that's about 700 'cfm' if the classroom has 10 m² of open windows you're fine, even an undetectable draft of 0.03 m/s is sufficient, but if it has 1 m² you need a barely detectable breeze of 0.3 m/s, if it has 0.1 m² you need a pretty noticeable breeze of 3 m/s ('light breeze' on the beaufort scale), and if it has a little 100-mm-square register you need 30 m/s which is a 'violent storm' on the beaufort scale (above 'whole gale') at 'fresh breeze' (8–11 m/s) you need 300–400 cm² of window well designed ventilation systems can provide this kind of airflow while controlling the temperature and humidity but they are at a big disadvantage because 300–400 cm² of window is a lot smaller than 300–400 cm² of duct sometimes that's not what matters most tho

sireat 4y ago

I was surprised how well a large modern building ventilates CO2. We had some employees complain about feeling "stuffy" when air conditioning was turned off(due to budget constraints). So maintenance brought their own CO2 meter and I brought my trusty Aranet4. Both our readings were around 650 in a medium sized office with 4 people. Apparently the raise of temperature from 22C to 26C was enough to trigger internal "stuffiness". PS By comparison my bedroom regularly reaches 3000 in the mornings if no windows are left open.