Continuous Emission Monitoring Systems: a compliance & integration guide

A Continuous Emission Monitoring System (CEMS) is the regulated chain from sample probe to certified report — analyzers, sample conditioning, data acquisition (DAS), and the secure link to the regulator.

Under CPCB directions in India and 40 CFR Part 60/75 in the United States, operators must demonstrate calibration evidence, drift correction, and a minimum data availability — usually 85–95% depending on pollutant and sector.

The CEMS DAS is the audit surface: it ingests analyzer raw signals, applies the calibration curve, flags out-of-spec data, and pushes time-stamped 15-minute averages to CPCB CARE-Air or the equivalent state portal.

Integration mistakes we see most often: mis-matched span gases, missing tamper detection on the manifold, and DAS clocks that drift relative to the analyzer clock — each one shows up as a non-conformance in the next audit.

Our recommended architecture pairs reference-grade analyzers (NDIR, UV-DOAS, paramagnetic O2) with an edge DAS that holds 60 days of raw data locally and replays missed packets after a network outage.