Monona,
I have no reason to doubt your word (indeed, I trust it implicitly) and we are all bound by having zero information here, but I can’t see the CO2 being the cause here.
Again, no evidence/info - but if the blood work of 19 people transported to the hospital showed elevated CO2 levels then I’m hard pressed to figure out why that wouldn't appear in the reports.
So assuming a 10 foot ceiling, that’s 9,000 cubic feet = 254,852 liters. Ideal gas law gives us 22.41 L/mol, so in round numbers there are 11,372 moles of air in that classroom.
If we bring in a kg of dry ice (again, how much does one bring into a classroom?) and flash evaporate the entire thing that’s (1,000 g) / (44 g/mol) = 22.73 mol CO2.
That would get you to 2,000 ppm. And since CO2 is heavier than air and tends to pool I suppose you can make the argument that at floor level they could be significantly higher…but that would be around their feet rather than noses..or were they all sitting on the floor? - here’s a nice demo:
https://www.youtube.com/watch?v=sspIq_pzPaw
But this is for an instant evaporation with zero air turnover. In reality, it would take place over many minutes if not a half hour and there’s going to be at least some air turnover during that time even with a closed door and 1 or 2 air changes per hour (as opposed to the 4-6 that’s generally recommended)
Now that I ponder this lack of information more, I’m wondering if one kid felt nauseous (for whatever reason), and they decided just to send the whole class to the hospital just to be safe (or to CYA, if you’re more cynical.
But again, working in a vacuum here. Obviously, the school should be doing a full follow up with the amount of material, HVAC etc. all being scrutinized….but nothing in the media, so who knows. I don’t think we will ever get more info on this case.
Rob Toreki
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On Feb 25, 2024, at 2:27 PM, Monona Rossol <0000030664c37427-dmarc-request**At_Symbol_Here**LISTS.PRINCETON.EDU> wrote:
Re, the particular dry ice experiment, I use several cases in my teaching in which people died from doing this kind of nonsense when the ventilation was not up to removing the CO2 rapidly enough.
I've thought about this kind of problem for decades. And I've hazcom-trained teachers including science teachers in grade schools and high schools. You can't ask them to do a risk assessment. They don't know even the most rudimentary things about how the chemicals interact with our bodies, basic physics, PPE, or ventilation. In fact, many of them have myths and misconceptions about health and safety that they also pass on to their students.
