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Delhi Air Pollution: ‘Many Air Monitoring Stations Not Working,’ Says Amicus; Supreme Court Seeks CAQM Report

In brief: During a November 3, 2025 hearing, the Supreme Court heard that a large share of Delhi’s official air-quality monitoring network was not fully functional during Diwali — a critical pollution period — and asked the Commission for Air Quality Management (CAQM) to file a detailed report explaining the lapse and what pre-emptive steps are being taken. This raises questions about how authorities trigger the Graded Response Action Plan (GRAP) when monitoring coverage is incomplete.

Sources: Supreme Court hearing coverage and CAQM/GRAP documentation. 0

Why this matters: accurate data is the backbone of pollution action

The Graded Response Action Plan (GRAP) — the staged emergency framework used across Delhi-NCR — is activated based on measured and forecasted Air Quality Index (AQI) values. If measurement stations are offline or producing unreliable readings, officials lack the real-time evidence needed to trigger stages of GRAP quickly and uniformly across the region. That means communities may not receive timely warnings, and regulatory steps (like construction curbs, vehicle restrictions, or bans on certain fuels) may be delayed until damage is already done.

GRAP and CAQM guidance explain stage triggers and duties of monitoring and action. 1

What the court was told

During the hearing, an amicus — a court-appointed counsel presenting the public interest angle — told the bench that “many” monitoring stations were not functioning during the Diwali period. Multiple media reports from the hearing quoted figures used in court: of 37 official stations in Delhi, only nine were reportedly working on Diwali days. The bench asked the CAQM and the Central Pollution Control Board (CPCB) for an affidavit explaining which stations were offline, why they were offline, and what remedial steps are in place to ensure continuous monitoring going forward.

Coverage of the hearing and the figure reported to court (9 of 37 stations functioning) were published by several outlets. 2

Short-term consequences seen on the ground

Practical effects of missing or unreliable data show up immediately: GRAP stages may be invoked late or inconsistently; local administrations may not receive the automated triggers they rely on; and public messaging becomes muddled. After Diwali this year, Delhi recorded widespread “very poor” AQI values across multiple locations — underscoring the stakes when monitoring gaps exist.

Reported AQI averages and observations from the period were summarized in local coverage. 3

How monitoring networks can fail (real-world examples)

Air-quality monitoring systems are complex: they require calibrated instruments, uninterrupted power and data links, routine maintenance, certified staff, and periodic calibration against reference standards. Common failure points include:

• Power or data-link outages at the site (local grid failure or poor telecom connectivity).
• Sensor drift or fouling from dust, moisture or insect ingress.
• Delayed calibration or lack of certified technicians.
• Procurement delays for spare parts or new stations during warranty/contract lags.
• Administrative gaps — unclear lines of responsibility among municipal bodies, state pollution control boards and central agencies.

Past RTI and audit reports from various cities have repeatedly flagged staffing shortages and slow maintenance as causes of intermittent station downtime. Without a published station-status log that is visible to regulators and the public, problems can be hidden until a crisis like Diwali draws attention.

Previous reporting and RTI disclosures have highlighted staff and maintenance gaps in monitoring networks. 4

The technical and legal framework: GRAP explained

The Graded Response Action Plan (GRAP) is the legal-operational playbook for Delhi-NCR during pollution seasons. It divides actions into staged responses (e.g., Stage I: Poor, Stage II: Very Poor, Stage III: Severe, Stage IV/Severe+: worst), each tied to AQI thresholds and a set of mandatory measures — from increased dust control and bans on certain construction activities to vehicle curbs and school closures in extreme situations. The CAQM maintains the GRAP orders and issues stage-based directions; CPCB and IMD/IIT teams supply forecasts and data inputs that inform those decisions.

The CAQM site and the official GRAP schedule detail stage triggers and measures. 5

Major drivers of Delhi air pollution — quick recap

Multiple long-standing sources combine in winter to create severe smog episodes:

1. Farm stubble burning in Punjab, Haryana and western Uttar Pradesh — seasonal crop-residue fires emit large quantities of PM2.5 and PM10 that travel into Delhi on prevailing winds.
2. Local sources — vehicle emissions, diesel generators (DG sets), brick kilns, and construction dust contribute continuously.
3. Domestic sources — use of biomass, coal, and inferior fuels in informal eateries and some households increases winter pollution peaks.
4. Meteorology — low wind speeds, temperature inversions, and stable boundary-layer conditions trap pollutants near the surface in winter months.

Any effective response must combine immediate measures (like GRAP steps) with medium- and long-term interventions (cleaner fuels, vehicle electrification, crop-residue solutions, and industrial controls).

What the CAQM and CPCB can — and should — show the court

To restore confidence in public reporting and enforcement, the Supreme Court’s demand for a CAQM affidavit makes sense. A useful report would include:

• a current, station-by-station operational status (online / offline / degraded), with timestamps;
• maintenance logs and calibration certificates for each Continuous Ambient Air Quality Monitoring Station (CAAQMS) over the past six months;
• root-cause analyses for any outages (power, instrument, staffing, procurement delays);
• an action plan with timelines to restore and strengthen monitoring coverage (replacement, redundant power/data links, mobile monitors);
• a transparency commitment — a public dashboard updated hourly that flags station health and network coverage so citizens and officials see gaps in real time.

Are monitoring gaps unusual?

Short-term outages are not unheard of — weather, vandalism, telecom faults and equipment issues happen — but the size and timing of outages matter. Several media accounts suggested that only a minority of stations were reporting during Diwali, a time of unusually high emissions. That timing magnifies the political and health consequences of any data gaps: Diwali-related burning, fireworks and other activities spike particulate loads, so missing data precisely when pollution peaks reduces the ability to act pre-emptively under GRAP.

Reports from the hearing and subsequent coverage noted the Diwali timing and the 9/37 figure. 7

Health implications when the network fails

When monitoring networks are incomplete, vulnerable groups—children, elderly, people with respiratory or heart disease—face both higher exposure and lower warning. AQI alerts and school/health advisories are driven by monitored data; if decisions are delayed or not taken because the network appears to show better conditions than reality, preventable exposures increase. Moreover, researchers and public health bodies use measured data for short-term epidemiology; gaps reduce the accuracy of risk estimates and the ability to target public-health messaging.

Examples from recent events

Two practical examples show why continuous monitoring matters:

• Delayed GRAP invocation: If several monitoring sites in a particular zone are offline, that zone may not cross the AQI threshold that triggers Stage II or III even though adjacent areas do — leaving local activities unchecked while pollution spreads.
• Indoor-outdoor mismatch: A viral clip last week demonstrated indoor AQI jumping from acceptable to hazardous in seconds when a door was opened to outdoor air; that kind of rapid change is better captured when a dense network of local monitors is functional and transparent. Public warnings and advice on ventilation, travel and masking depend on such granularity.

Examples and video reporting about indoor-outdoor AQI changes were covered in local media. 8

What citizens can do now (practical, immediate steps)

Even while authorities sort monitoring and enforcement, individuals can reduce exposure and help reduce emissions:

• Track multiple AQI sources (CPCB/CAQM dashboards, and independent networks like SAFAR/other community monitors) — compare them to identify consistent patterns.
• When AQI is ‘poor’ or worse, avoid strenuous outdoor exercise, use N95/FFP2 masks outdoors, and keep vulnerable people indoors with filtered air if possible.
• Reduce local emissions: prefer cleaner cooking fuels, avoid burning garden/household waste, and use public transit or carpool where feasible.
• Report visible issues: smoke from nearby burning or industrial releases can be reported to municipal hotlines or pollution-control boards with photos and timestamps.

Longer-term policy fixes the court and agencies should consider

Policy choices that strengthen both monitoring resilience and pollution control include:

1. Redundancy and diversification: Invest in spare sensors, backup power and multiple data links (cellular + wired + satellite where needed) for each critical station.
2. Network densification: Alongside 37 or 46 reference stations, add low-cost sensor grids (properly calibrated and corrected) to provide neighbourhood-level granularity.
3. Transparent public dashboard: Publish an hourly station health and data-quality feed so citizens and researchers can flag anomalies quickly.
4. Maintenance contracts and staffing: Ensure third-party contracts include fast-reaction maintenance clauses and that state and central agencies maintain trained technicians on retainer.
5. Legal accountability: Build monitoring uptime targets into CAQM/CPCB performance metrics and link remedial funding to compliance.
6. Community involvement: Support community monitoring programs that are trained, audited and integrated into official datasets so they supplement—not replace—reference stations.

How the GRAP plays out in practice — recent official moves

When air quality deteriorates, CAQM and local bodies invoke GRAP stages. For instance, in October 2025 the CAQM invoked a Stage II 12-point action plan to try to prevent escalation after forecasts indicated deterioration. Practical measures under Stage II have ranged from intensified dust control to restrictions on certain polluting activities. Having timely, reliable station data is essential for these actions to be targeted and proportionate.

CAQM orders describing stage-based actions and recent Stage-II invocation are published on the CAQM and PIB pages. 9

Questions readers are likely to ask — answered

Q: If stations were offline, can mobile monitors or satellites help?

A: Mobile monitoring units (mounted on vehicles or temporary trailers) and low-cost portable sensors can fill short-term gaps. Satellites provide regional-scale aerosol information but cannot replace ground-level, calibrated PM2.5/PM10 readings required for GRAP triggers. Best practice is to use satellite and model data to flag potential hotspots, then deploy mobile monitors to validate ground truth.

Q: Who is legally responsible for maintaining the stations?

A: Responsibility varies. Reference CAAQMS installations are often funded by central agencies but operated by local authorities or contracted firms. CAQM, CPCB and state pollution control boards coordinate; the precise custodianship of each station should be listed in a network register that CAQM or CPCB can produce for the court.

Q: Will fixing monitors fix the pollution?

A: No — but it helps. Monitoring is about detection, accountability and timely action. Fixing monitors makes the system transparent and enforces rules more fairly. Actual pollution reduction requires cleaner fuels, industrial controls, alternate crop-residue management, transport policies and long-term urban planning.

What a robust monitoring dashboard should show

An ideal public-facing dashboard would include:

• Real-time AQI per station and rolling 24-hour averages.
• Station health indicators (online/offline, data quality flags, last calibration date).
• GRAP stage triggers with timestamps and linked orders issued by CAQM.
• Forecasts (IMD/IITM) with probabilities for ‘very poor’ or worse days.
• Historical comparisons and maps that allow neighbourhood-level filtering.

What the Supreme Court’s direction could lead to

If the court asks CAQM and CPCB for a detailed affidavit and the agencies comply, we could see several outcomes in short order:

• Immediate maintenance and audit schedules published, with timelines to bring all stations to working order.
• Temporary deployment of mobile monitors to fill data gaps in critical neighbourhoods.
• Stronger monitoring uptime requirements embedded into CAQM/CPCB orders and public performance reporting.
• Heightened public scrutiny leading to faster GRAP action when forecasts warn of deterioration.

Limitations and trade-offs to consider

Investment in monitoring must be paired with action. Expensive reference stations need upkeep; low-cost sensors are cheaper but require calibration to be useful for regulatory triggers. Also, the court-ordered processes take time; immediate public-health guidance should rely on available data and conservative assumptions where gaps exist (i.e., err on the side of caution and trigger GRAP measures when in doubt).

International context — how other cities pair monitoring and action

Global cities facing winter smog (e.g., Beijing, Lahore at times) combine dense sensing grids with strict short-term measures and long-run structural reforms (fuel standards, vehicle controls, cleaner heating). Many successful programs emphasized transparent data publication and localized action plans tied to neighbourhood exposure. Delhi can adopt similar layered approaches adapted to its governance reality.

Independent monitoring and citizen science

Community-driven sensor networks have proliferated. They are valuable for showing local variation and prompting action, but data quality varies. The CAQM and CPCB can harness community data by establishing protocols for calibration, quality checks, and integration into official datasets — a hybrid model that multiplies spatial coverage while retaining regulatory confidence.

Actionable checklist for local officials (quick reference)

• Publish station health list within 48–72 hours.
• Deploy mobile monitors to neighbourhoods with no coverage.
• Invoke precautionary GRAP steps when forecasts show likely deterioration, regardless of limited station coverage — use regional signals from IMD/IITM.
• Start immediate procurement for spare parts and maintenance contracts where bottlenecks exist.
• Commit to a public, hourly dashboard for station status and AQI.

Possible follow-ups readers may watch for

• The CAQM affidavit to the Supreme Court and any annexures listing station health and maintenance logs.
• Updates to the CAQM GRAP orders (revocations or invocations with explicit stage reasons).
• Deployment notices for mobile monitoring and timelines for commissioning new/replacement CAAQMS units.

Concluding thoughts

Reliable air-quality monitoring is not a technical luxury — it’s a public-health necessity. The Supreme Court’s intervention highlights that data integrity matters, especially during predictable pollution spikes like Diwali season. Fixing monitors won’t alone clear Delhi’s air; but without trustworthy data, mitigation becomes reactive, uneven and less defensible. The court’s demand for a CAQM report gives authorities a clear accountability moment: publish, fix, and strengthen the network so that GRAP and other measures can be triggered with confidence and fairness.

Key takeaways

• Only a minority of official monitoring stations were reported functional during Diwali; the Supreme Court has asked CAQM for a detailed report. 11
• GRAP depends on accurate, timely data — missing stations make pre-emptive action harder. 12
• Short-term fixes (mobile monitors, transparent dashboards, rapid maintenance) plus long-term structural reforms are both required.
• Citizens can reduce exposure immediately by following multiple AQI sources and using protective measures when levels spike.