Humans in isolation can tolerate 400ppm. Offices and houses accumulate far more than outside it pushes to far higher inside, enough to breach health and safety

Humans in isolation can tolerate 400ppm. Offices and houses accumulate far more than outside it pushes to far higher inside, enough to breach health and safety recommendations, cause decreased performance and so on. We don't know where planetary equilibrium would settle at 400ppm as we're still emitting. Looking outside and no longer in isolation >400 seems to be causing some pretty wild changes. I'd say that's far from zero problems.