Carbon dioxide (CO2)

Carbon dioxide

Stasis Home Research Every claim on this page is graded against peer-reviewed health research and linked to its primary source.Updated June 2026

Indoor CO2, carbon dioxide, the gas everyone breathes out, is a marker of how well a room is ventilated. The reading tracks how much fresh outdoor air reaches a room relative to the people breathing in it.

What does Carbon dioxide (CO2) mean?

Carbon dioxide is the colorless, odorless gas every person exhales. What the indoor number tells you is how well a room is ventilated. It rises when the people in a space exhale faster than outdoor air can replace the stale air, and it falls the moment the air exchanges. ASHRAE, the engineering body that sets ventilation standards, reads it that way, and so do the EPA and WHO. It shows up in a home audit because by morning a closed bedroom in a tightly sealed modern build can climb well past the fresh-air baseline you would breathe on an outdoor walk. The fix is mechanical. You move more outdoor air through the room: open the door, crack a window when the outdoor air is clean, run a fan. The building outpaced its ventilation, and the room is the part you control.