[switch007]

Your comment doesn't seem to match up with https://www.kane.co.uk/knowledge-centre/what-are-safe-levels... unless you mixed up CO and CO2? Am I missing something?

EDIT: ah, looking at a CO2 monitor, it says "Indoor air quality: Good (0 to 800ppm), Normal(800 to 1200ppm), Poor (>1200ppm) indication"