Data-logging indoor air quality meter that tracks CO2 (via NDIR sensor), temperature, and relative humidity on a triple-value LCD, with an internal memory capable of storing up to 32,000 time-stamped readings. It calculates time-weighted average and short-term exposure limit values, useful for verifying HVAC performance or monitoring air quality in schools, offices, and industrial spaces. This unit includes a NIST-traceable calibration certificate.