600ppm is the place where it start affecting human cognition from what i recall. there was a dude in the reddit back in the day called MrVisible that was obsessed with this and had a whole sub about it . i thing it was called r/doomsdaycult or something like that.
EDIT: i just went to find that old sub and reddit banned it of course . maybe a reddit archive will have it.
600ppm is the place where it start affecting human cognition from what i recall. there was a dude in the reddit back in the day called MrVisible that was obsessed with this and had a whole sub about it . i thing it was called r/doomsdaycult or something like that.
EDIT: i just went to find that old sub and reddit banned it of course . maybe a reddit archive will have it.