Indoor Air Quality Logger

Field guide: Indoor Air Quality Logger

CO₂ is the honest snitch of indoor air: people exhale it at a known rate, so the concentration in an occupied room is a direct readout of how much fresh air the ventilation actually delivers — under ~800 ppm means generous outside air, 1,000 is the classic 'adequate ventilation' line (roughly 700 ppm above outdoor per ASHRAE-derived practice), and the 1,800 ppm classroom at 2 p.m. explains the afternoon brain fog with a number. This logger builds those room-by-room profiles: occupied-hours readings, flags, trends.

The companion parameters complete the diagnosis: PM2.5 indoors (held to the WHO 24-h guideline of 15 µg/m³ as a health-honest target) splits into 'leaking in from outside' versus 'generated inside' when you compare rooms and hours; humidity's 30–60% band is the mold-versus-static corridor, with sustained readings above 60% in any corner being the mold-risk finding worth acting on before the smell arrives. For facility managers, dated per-room logs are the IAQ-complaint response that turns arguments into airflow work orders.

Field tips

• Measure at breathing height, away from windows, doors and people's direct exhalation — a sensor on the teacher's desk reads the teacher.
• Log rooms at peak occupancy; an empty room at 420 ppm proves nothing about the 30-person meeting at 3 p.m.
• If CO₂ is fine but the room still feels stuffy, log temperature/RH — 'stuffy' complaints are humidity-and-heat as often as they're air.

Records are stored only in this browser (localStorage) — export regularly. This tool aids field documentation; it does not replace your agency's official inspection procedures or engineering judgment.