Ooh, exciting!

We have a local farm where you take apples and they press and bottle apple juice - lovely, see if you have one local to you...

I would definitely say that only the data from 1 of the 4 classrooms indicates good per-person ventilation. 'Very bad air quality' is too vague - I think the paper I cited above might provide the exact corresponding values of mean CO2 values, if that's what you're interested in ...

Without knowing occupancy and window opening some of your suggestions (e.g removing 11:30-14:00) would result in lowering the dailly mean CO2 reported - certainly the much talked about 'lunch hour' makes a non-significant difference on the vast majority of days shown.

Before you get going about your favourite 'lunch hour', zoom into the attached figure (from doi.org/10.1016/j.jo...) notionally similar classrooms and occupancy - so ventilation behaviour has a leading order effect.

We know the schools are operational on the days analysed and the monitors are placed in occupied classrooms - in case you are unaware, UK schools don't have loads of empty classrooms just kicking around...

The article goes to great lengths to infer ventilation rates concluding the attached - these rates account for inoccupancy and are far more meaningful than CO2 thresholds. The fact these are low and adherence high is the best evidence for the need of changing things for the better...

This is a research article, not an opinion piece - only reporting fact allowed, not passing personal opinions on guidance is suitably. On X, I've made it clear that the BB101 thresholds are not we should be aiming for but, for now, they are the guidance. More importantly, you miss the point...

Loads more findings within - my fav is that CO2 levels are statistically differ within primary and secondary schools but translating to per-person ventilation shows there is no difference as the latter appropriately accounts for differing generation rates of different age groups.

we also use the analysis published here doi.org/10.1016/j.bu... to demonstrate that the associated per-person ventilation rates are low (relative to almost all available guidance).