CEMS — Continuous emissions monitoring

Data acquisition and hourly values

• SO₂, NOx, CO, CO₂, O₂, particulate matter, stack flow, stack temperature and moisture.
• Hourly values each clock hour: an operating hour is valid only with at least one valid minute of data in each 15-minute quadrant (§75.10(d)).
• EPA Method 19 F-factor calculations for lb/MMBtu, lb/h, heat input (MMBtu/h) and ppm corrected to reference O₂.

Limits and calibration

• Permit limits on 1-hour, rolling 3-hour, 24-hour and rolling 30-operating-day averages; exceedances raise alarms and are recorded with start, end, hours and maximum, and engineers record cause and corrective action.
• Daily calibration drift (zero and span, % of span): ≤ 2.5 % passes, 2.5–5 % needs adjustment, > 5 % fails; the monitor is out of control from a failure until the next pass, and also after 26 hours without calibration (Part 75 Appendix B).

Missing data and reports

• Substitution during missing or out-of-control periods per Part 75 §75.33 (before/after average, 90th/95th percentile lookback, maximum lookback, maximum potential value), each value tagged with its method code (MODC).
• Quarterly excess emission and monitor downtime report (§60.7(c)(d)) with operating hours, heat input, tons emitted, exceedances, downtime by parameter, data availability and calibrations, exportable to CSV.

Tamper evidence

• Each hourly record is linked to the previous one by SHA-256, and each day's chain head is written into the platform's audit hash chain; "verify record chain" recomputes it and detects any change.

Industries

• General & discrete manufacturing

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