Reducing CO₂ indoors: the ventilation ladder
CO₂ is what people exhale. The only durable answer is moving more outside air in. First find out why it stays high, then work the cost-ordered ladder, from free to capital project.
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Office IAQ: the 4 p.m. conference-room problem
A typical office starts the day near the outdoor CO₂ level and ends it well above 1,000 ppm in the meeting rooms, plus VOCs from cleaning and new furniture and whatever the outdoor air brings in.
CO₂ rebreathing detection: when a room is breathing itself
A near-linear CO₂ climb that does not decay is the signature of a room rebreathing its own air. The math is straightforward and the pattern is unmistakable on the dashboard.
Cognitive effects of CO₂: the Allen and Satish literature
Two landmark chamber studies (Satish 2012, Allen 2016) show executive function dropping monotonically as CO₂ rises from 550 to 1,400 ppm. The shape, the domains, and the mechanism candidates.
CO₂ as an airborne-pathogen proxy: what the ratio actually tells you
CO₂ does not measure pathogens. But CO₂ and exhaled pathogen droplets share a source (occupants) and a sink (ventilation), so the indoor-to-outdoor CO₂ ratio tracks the fraction of air in the room that other people have already breathed. This is why the Aranet model was widely adopted for ventilation monitoring during the pandemic.
CO₂ sensor accuracy and ventilation
CO₂ is the clearest occupancy and ventilation signal in most rooms, but placement, calibration assumptions, and recovery time still shape the interpretation.
