Clear explanations of what indoor-air measurements mean, what they cannot tell you, and what to do when a room starts behaving strangely.
Measurement guides
Start with the air people breathe out.
One subject at a time, checked against primary and authoritative sources.
CO₂12 min read
Your CO₂ monitor says 1,400 ppm. What does that actually mean?
Why bedrooms climb overnight, where the famous 1,000 ppm number came from, why a purifier cannot fix it, and how to respond without treating one reading as a diagnosis.