The Central Pollution Control Board (CPCB) has issued a revised calibration protocol for Online Continuous Emission and Effluent Monitoring Systems (OCEMS), setting standardized requirements for a range of parameters to ensure the accuracy and reliability of environmental data. These guidelines, effective from July 2025, specify the frequency and procedures for calibration, checks, and performance testing for emissions and effluent monitoring systems.
Emissions Monitoring Standards
Particulate Matter (PM)
Initial calibration is required upon installation by the instrument supplier. A quarterly, in-house calibration check is mandated, along with annual performance testing by an EPA Recognized or NABL Accredited laboratory. If comparison values (dust factor) show a deviation of more than 10% for two consecutive monitoring periods, the system must be recalibrated.
Gaseous Emissions
Initial calibration is to be performed by the supplier. In-house checks are required every fortnight for two-point calibration and every three months for multi-point calibration. Annual performance testing must be conducted by an EPA Recognized or NABL Accredited lab. The protocol permits the use of certified portable gas analyzers, in addition to certified gas cylinder-based audits, for calibration.
Effluent Monitoring Standards
Temperature and pH
Initial calibration is to be performed by the supplier. Fortnightly in-house calibration checks are required. Annual performance testing must be conducted by an EPA Recognized or NABL Accredited lab. Recalibration for temperature is necessary if values deviate by more than +/- 1 Degree Celsius for two consecutive monitoring periods. For pH, recalibration is needed if values deviate by more than +/- 0.2 from a certified reference material for two consecutive monitoring periods.
BOD, COD, TOC, TSS
Initial calibration is performed by the supplier. Monthly in-house calibration checks are required. Annual performance testing must be conducted by an EPA Recognized or NABL Accredited lab. Recalibration is mandated if comparison values deviate by more than +/- 20% from lab results for two consecutive monitoring periods.
For all parameters, incidental calibration is also required following any major system repair, change of lamp, or realignment. These standardized protocols are expected to enhance the credibility of environmental data and support more effective pollution control measures.