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

Yeah, that really makes me rethink my entire education experience...

...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?

The utopia of adequate ventilation.

A cynical view is - with better CO2 levels the outcome of those political/military decisions could be worse.

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.

They are legally required in the primary bedroom of all new build houses in Scotland, possibly also in England and Wales.

Huh? Really? Are you thinking of Carbon Monoxide detectors, perhaps? Sometimes these are incorrectly called "CO2 detectors".

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-do...

Well done, Scotland.

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.

New houses in The Netherlands have a monitor in each room (bedrooms, kitchen, living room and bathroom/shower) that control the mechanical ventilation.

In fancier homes they can control the ventilation per room, though the standard is that they control the ventilation for the entire house.

They are part of the sensor suite in big buildings.[1] The usual sensor set is temperature, humidity, and CO2. It's mostly hotels with conference rooms that are serious about this, because their product is comfortable conferences.

As buildings approach airtightness, this becomes essential. I was expecting more in this area from the IoT crowd, but they never delivered. It's the old-school HVAC systems which do this.

Some years back I went to an IoT meeting in San Francisco, in a beautifully converted industrial building in Dogpatch on the waterfront. Big windows and skylights, with openable windows driven by manual chain falls on both. Ceiling fans. Plus a standard HVAC system. Was all of this coordinated in any way? No.

The place should have had motor drives on the windows. They were all on two long shafts, so it wouldn't be all that hard. As the place filled up with people, the skylights should be opened and the ceiling fans driven to blow upward and exhaust hot air and C02. Open the bay-facing windows slightly for intake air. As the evening went on and outside temperature dropped, close the bay-facing windows, continuing to monitor CO2 and temperature. If heating, open a damper to take air from the outside as necessary to keep the CO2 down. When everybody leaves, flush the air for a few minutes, then close everything up, turn off the fans, and let the temperature drop a few degrees.

The place should have been a showpiece for intelligent building control. But what were they pushing? Refrigerators with a tablet built into the door, for more than the cost of a refrigerator plus an iPad. The tablet had no useful interaction with the refrigerator; it was just a general use tablet.

Even home "smart thermostats" don't do much. They need this set of sensors, plus an external air damper so they can switch from recirculate to outside air as necessary. And the ability to run fans, without AC or heat as necessary. But that requires actual installation, which neither Amazon nor Apple can competently handle.

All this stuff saves enough energy to pay for itself.

[1] https://buildings.honeywell.com/gb/en/products/by-category/s...

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.

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.

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/

"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.

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

(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

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.