Q.01

Which industries need continuous emission monitoring in India?

India requires continuous (online) emission monitoring in the 17 categories of highly polluting industries, at Common Bio-Medical Waste and Common Hazardous Waste incinerators, and on boilers in a further list of industries. CPCB's 1st Revised Guidelines for Continuous Emission Monitoring Systems (August 2018) say these industries "have to install Continuous Emission Monitoring System". Industries outside the 17 categories "should consider" CEMS as a tool of self-regulation, but are not required to install it.

Legal basis

  • CPCB directions of 05.02.2014 (letter No. B-29016/04/06PCI-1/5401), issued under section 18(1)(b) of the Water and Air Acts to the State Pollution Control Boards and Pollution Control Committees. They require online emission and effluent monitoring in the 17 categories, CETPs, STPs and the common incinerators. Online data goes to both the state board and CPCB. The original deadline was 31 March 2015, later extended to June 2015.
  • G.S.R. 96(E), 29 January 2018 (MoEF&CC, under the Environment (Protection) Act 1986) requires CEMS on boilers.
  • CPCB's FAQ also cites directions under section 5 of the E(P) Act. It says failure to comply "may lead to closure of the units". It adds Grossly Polluting Industries (GPI) in the Ganga Basin to the sectors directed to monitor online.

The 17 categories and their emission parameters (Annexure-I of the 2018 guidelines)

CategoryCEMS emission parameters
AluminiumPM, Fluoride
CementPM, NOx, SO2
DistilleryPM
Dye and dye intermediatenone listed
Chlor-alkaliCl2, HCl
FertilizersPM, HF, Ammonia
Iron & steelPM, SO2, NOx
Oil refineryPM, CO, NOx, SO2
PetrochemicalPM, CO, NOx, SO2
Pesticidesnone listed
Pharmaceuticalsnone listed
Power plantsPM, NOx, SO2
Thermal power plantsPM, NOx, SO2, plus gaseous mercury where the environmental clearance (EC) stipulates it
Pulp & papernone listed
Sugarnone listed
Tannerynone listed
ZincPM, SO2
CopperPM, SO2

The annexure also lists Textile (GPI), Dairy (GPI) and Slaughter House with no emission parameters, and Boilers with SO2, NOx and PM. Thermal power plants are a sub-row under Power Plants, so the table has 17 categories. The common hazardous and bio-medical waste incinerators must monitor PM, NH3, SO2, NOx and other sector-specific parameters.

Boilers under G.S.R. 96(E) CEMS is required on boilers used in these industries: Sugar, Cotton Textile, Composite Woollen Mills, Synthetic Rubber, Pulp & Paper, Distilleries, Leather, Calcium Carbide, Carbon Black, Natural Rubber, Asbestos, Caustic Soda, Small Boilers, Aluminium Plants, Tanneries, Inorganic Chemicals "& other such industries using boilers".

Key operating obligations in the guidelines

  • Each unit is responsible for submitting its own data and must ensure at least 85% data availability.
  • Faults must be fixed within 72 hours, or SPCB and CPCB must be notified.
  • Performance audits must be done by an empanelled independent third-party laboratory, not by the industry itself.
  • Units claiming Zero Liquid Discharge must install PTZ IP cameras and flow meters at their disposal points.

Maharashtra in practice: the Maharashtra Pollution Control Board's public Online CEMS registry includes registrations in Chemical, Distillery, Sugar, Pharmaceuticals, Iron and Steel, Cement, Thermal Power Plant, Aluminium, Fertilizers, Petrochemicals, Oil Refinery, Zinc, Pesticides, Dye-intermediates, Textile, CETP, CHWTSDF and Bio-Medical Waste, among others [1][2][3][4].

I found reports of later CPCB updates (a July 2025 calibration protocol and a new portal at cems.cpcb.gov.in), but only on non-official sites. I could not confirm them from CPCB's own text, so the above reflects the 2018 guidelines and the FAQ.

Approach: I searched the MoEF Gazette notification archive (1986-2017) and the Maharashtra Online CEMS registry, then read CPCB's official CEMS guidelines and FAQ. The 2014 CPCB direction and G.S.R. 96(E) themselves are not in the datasets; the guidelines summarise both.

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Q.02

What does Maharashtra require for online emission monitoring?

Maharashtra applies the CPCB online-monitoring obligation for the 17 categories of highly polluting industries and adds its own rules for connecting to the state server. Industries must register on the MPCB Online CEMS portal. They "should set up" separate online systems for effluent, emission and ambient air quality, and must send every parameter in the CPCB guidelines to MPCB's real-time server at a 1-minute frequency. MPCB has enforced this: in 2016 it circulated CPCB closure directions against 295 units in the 17 categories in Maharashtra for not installing online monitoring.

What MPCB requires (from its Online CEMS page, SOP and FAQ)

  • Registration: Each industry fills in an online pre-deployment checklist at the MPCB registration page. MPCB's central software team verifies the parameters, creates a site ID and monitoring station IDs, and emails the upload URL and login details. The industry or its vendor configures its software, tells MPCB it is ready, and gives MPCB remote login access so MPCB can check that data is arriving.
  • Parameters: "All parameters specified as per CPCB guidelines has to be sent to MPCB."
  • Frequency: "Transmission has to be at 1 Minute frequency". Each 1-minute value is an average of readings polled every 10 seconds, sent with ISO 7168 data quality codes (for example D for calibration drift, C for calibration mode).
  • Delayed data: Data sent more than 15 minutes after it was recorded must go through the delayed-data URL with quality code "L". Otherwise "feed will be rejected". Timestamps use yyyymmddhhmmss.
  • Transmission format: No FTP; uploads must use HTTP REST. Each monitoring station sends its own zip file, named SiteID_MonitoringID_UploadTime.zip, in the format set by MPCB's Open API document. A test URL is provided for trial uploads.
  • Exceedance alerts: MPCB shows the industry how to respond to exceedance alerts. Industries can log in to see their data, alerts and notifications.
  • Cameras (Open API, 11 February 2021): Industries must install cameras to MPCB's specification and give MPCB an RTSP URL for live streaming. MPCB assigns each camera an ID. The industry's software must move the camera (left, right, up, down, zoom in, zoom out) when the MPCB server sends a command.

Enforcement history: The MPCB circular of 13 October 2016 is titled "To ensure compliance of the Closure directions issued by CPCB to 17 category of highly polluting industries for not complying with the proposed directions for installation of online continuous monitoring systems". Its annexure lists 295 Maharashtra units that received CPCB closure directions, mostly between January and August 2016. They were mainly sugar mills and distilleries, plus pharmaceuticals, dye and dye intermediates, iron and steel, fertilizer, pesticide, petrochemical, pulp and paper, and one cement unit. CPCB had withdrawn the direction for 17 of them.

What the Maharashtra registry shows: Each registration on the MPCB Online CEMS registry records, per parameter:

  • the monitoring type (Emission or Ambient)
  • the analyser make, model and measuring range
  • the standard limit
  • stack details and boiler type and capacity

For example, a thermal power plant registration in Chandrapur lists SOx in mg/Nm3 with a standard limit of 50 on a CFBC boiler [5]. A cement (RMC) site in Thane lists only ambient PM10 and PM2.5 [2].

What I could not read: Two MPCB documents linked from its Online CEMS page are scanned images that I could not open:

  • the circular of 6 April 2016 on uploading online monitoring data to the MPCB website
  • the direction of 22 March 2019 on installing remote calibration and performance testing

The cover page of the October 2016 circular is also a scan. So I can't give their exact wording, including any deadlines or calibration requirements.

Approach: I searched the MPCB Online CEMS registry and the MPCB Water and Air Act consent decisions, which hold registrations and consent grants but not the rules themselves. The requirements above come from MPCB's official Online CEMS pages and circulars.

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Q.03