India National Air Quality Monitoring Programme
What is India's National Air Quality Monitoring Programme?
India's National Air Quality Monitoring Programme (NAMP) is a nationwide ambient air quality monitoring network run by the Central Pollution Control Board (CPCB). As of 19 November 2024 it had 966 operating stations in 419 cities and towns across 28 States and 7 Union Territories (CPCB, About NAMP).
Objectives (CPCB)
- Determine the status and trends of ambient air quality.
- Find out whether the prescribed ambient air quality standards are being exceeded.
- Identify non-attainment cities.
- Build the knowledge needed to develop preventive and corrective measures.
- Understand how the environment cleans itself naturally: dilution, dispersion, wind-based movement, dry deposition, precipitation and chemical transformation of pollutants.
What is monitored and how often (CPCB)
- Pollutants: four are monitored regularly at every location: sulphur dioxide (SO2), oxides of nitrogen as NO2, respirable suspended particulate matter (RSPM/PM10) and fine particulate matter (PM2.5).
- Sampling schedule: stations run 24 hours a day, twice a week, which gives 104 observations a year. Gaseous pollutants are sampled every 4 hours, particulate matter every 8 hours, and PM2.5 over 24 hours.
- Weather data: wind speed, wind direction, relative humidity and temperature are recorded alongside the air quality readings.
Who does the monitoring
- State Pollution Control Boards, Pollution Control Committees and other reputed institutes carry it out.
- CPCB coordinates them to keep the data uniform and consistent, and gives them technical and financial help [1].
Published data
- CPCB publishes yearly NAMP results. The reports for 2015 and 2016 list SO2 readings station by station, with the number of monitoring days and minimum, maximum and annual average values [2][3].
- More recent reports combine manual and continuous monitoring into city-level annual averages. The 2021 report counts 1,257 stations, more than the 966 NAMP figure above because it includes continuous stations: 883 manual stations in 378 cities and towns, plus 374 continuous stations in 190 cities and towns [4].
- The 2024 report only includes data with at least 104 monitoring days. Besides SO2, NO2, PM10 and PM2.5, it adds annual averages for NH3 (ammonia) and benzene [1].
Approach: I used CPCB's yearly NAMP data reports (2013-2024) and CPCB's official "About NAMP" page. The data reports don't describe the programme's objectives or sampling schedule, so those come from the CPCB page.
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How do manual stations differ from continuous air quality monitoring stations?
Manual stations are CPCB's original NAMP network. They measure a small set of pollutants (SO2, NO2, PM10, PM2.5) by collecting samples that are analysed later. Continuous stations (CAAQMS) are automated, climate-controlled shelters full of analysers that measure a much wider set of pollutants around the clock. They log data in real time and feed the daily National Air Quality Index. CPCB merges the results from both into the annual NAMP figures.
| Manual stations | Continuous stations (CAAQMS) | |
|---|---|---|
| Pollutants | SO2, NO2, PM2.5 and PM10 are measured regularly at all locations (CPCB, Manual AAQ Monitoring Station in Delhi) | Most locations measure SO2, NO2, NH3, O3, CO, benzene, PM10 and PM2.5, plus weather readings (same CPCB document) |
| How measurements are made | Samples taken over 24 hours, twice a week, about 104 a year (CPCB, About NAMP, cited last time) | Automatic analysers in a shelter kept at 25 °C. Each gas analyser has its own unit, and PM is measured by beta-ray or TEOM monitors (CPCB CAAQM Technical Specifications, pp. 5, 10) |
| How fast results arrive | Annual summaries: the 2018-2020 reports list minimum and maximum 24-hour averages and an annual average per location [5][6] | Real-time. Data are recorded every few seconds and reported as 15-minute averages, with daily, weekly and monthly statistics. They are sent automatically to a central server at the State Pollution Control Board (CAAQM specs, pp. 14-15, 26, 31) |
| Calibration and quality checks | Not covered in the documents I read | Daily calibration checks, precision checks every two weeks, linearity checks every six weeks and a full calibration every three months, following US EPA methods. Data capture must be at least 90% of operating time, and alarms go off when automatic zero or span checks drift beyond ±5% (CAAQM specs, pp. 13-14, 32) |
| Public use | Trend and compliance assessment under NAMP | A daily AQI is produced for these stations and published on CPCB's website (CPCB Delhi document, p. 2) |
| Funding and rollout | Run by the State Boards and Committees, with CPCB coordinating and providing support | CPCB and the State Boards split the cost 50:50. Million-plus cities came first, then state capitals (CPCB Delhi document, p. 2) |
Network size and combined reporting
- In 2021 the network had 883 manual stations in 378 cities and towns. It also had 374 continuous stations in 190 cities and towns, giving 1,257 stations in total [4].
- The 2018-2020 data reports are labelled "Manual monitoring under National Ambient Air Quality Monitoring Programme" [7].
- From 2021, CPCB's annual tables combine data from both station types [8]. In 2024, a station's data counted only if it had at least 104 monitoring days [1].
- The two types can share a site. CPCB's ITO (BSZ Marg) station in Delhi does both manual and automatic measurement, and CPCB describes it as a model station (CPCB Delhi document, pp. 1-2).
Approach: I started with CPCB's annual NAMP data reports (2013-2024), which give station counts but don't explain how the two methods differ. For that I used two official CPCB documents: the note on its manual stations in Delhi and the technical specification for CAAQM stations.
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