How the sensor sees: optical CO₂ vs MOX
CO₂ is read by pulsing infrared light the gas absorbs and listening for the pressure wave. VOCs are read by watching a hot ceramic surface change conductance. Different physics, different limits.
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How interpretation works
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Cross-sensitivities: what confuses each sensor
Every sensor has things it sees that it shouldn't. Knowing the cross-sensitivities is how you read the right story in the numbers.
Why your reading differs from the nearest EPA monitor
Three reasons your number rarely matches the official outdoor AQI: hyperlocal variation, time resolution, and calibration class.
PM sensor accuracy and aerosols
Optical PM sensors estimate mass from scattered light. They are powerful for building telemetry, but aerosol chemistry and particle shape still matter.
VOC Index vs TVOC
VOC Index is a relative signal from a MOX gas sensor. TVOC is a concentration-style lab concept. They measure different things.
NOx Index vs NO₂
NOx Index is a combustion-pattern signal. It is not a regulatory NO₂ concentration measurement.
