Trust layer
Sources & methodology
Delhi Air Health should be useful because it is careful with uncertainty—not because it displays more decimal places.
Current + history layer
Current, owned history, OpenAQ and official AQI stay separate
The official CPCB resource on data.gov.in supplies the current station snapshot. When the optional archive is configured, Delhi Air Health stores successive snapshots from that same feed for its own descriptive time series. OpenAQ remains a separate hourly-history layer for the matched physical monitor. CPCB’s official AQI portal is linked as authoritative, but is not scraped into the product without a stable documented machine-readable endpoint.
Recent context
Missing hours stay missing
Individual campus pages request a bounded one-week OpenAQ hourly history for the matched physical monitor. The chart normalizes the last 24 completed hours and displays gaps instead of interpolating them. A “recent typical” PM2.5 value is shown only when at least three preceding 24-hour windows each have at least 16 valid hours.
Owned history archive
We store observations, not invented semantics
The server can archive one row per physical monitor and CPCB source timestamp. Duplicate collection runs are upserted rather than counted again. Because the OGD field is named `avg_value` without a sufficiently explicit averaging-window definition for this use, archived values are labelled reported snapshots. They are not converted into an official AQI or treated as validated one-hour means.
Long-term trends
City-level annual evidence stays separate from campus snapshots
Published CAQM/CPCB city-level annual series are used for Delhi. It does not back-project those annual numbers onto individual campuses, and it flags 2020 as COVID-affected rather than treating the lockdown year as a normal structural baseline.
Shared monitors
30 campuses do not mean 30 independent sensors
Nearby campuses can legitimately select the same monitor. The explorer makes that reuse visible, and the network trend deduplicates stations so a shared monitor is not counted repeatedly simply because several colleges are close to it.
AQI integrity
Reported PM average ≠ automatically an official AQI
The CPCB OGD resource exposes a field named `avg_value`, but its public metadata does not explicitly define that field's averaging window. Delhi Air Health therefore uses it as a reported particulate snapshot, not as proof of an official AQI. A PM-only index is calculated only when a matched 24-hour history has sufficient hourly coverage.
Activity guidance
Official category in, transparent interpretation out
The activity planner does not invent a go/no-go threshold from the current CPCB particulate snapshot. It uses a defensible AQI category when available, then combines CPCB health-impact wording with activity intensity, duration and established exercise-exposure physiology. The result is labelled as a Delhi Air Health interpretation, not an official CPCB prescription.
Campus comparisons
Compare monitors, not imagined campus microclimates
Current PM2.5 is compared only when both campus-linked references are current. If two campuses share one physical monitor, the comparison is explicitly marked non-independent. The output is a snapshot of ambient references, not a long-term or personal-exposure ranking.
Action layer
Reduce exposure; do not promise elimination
Particulate respirators and indoor filtration are treated as exposure-reduction tools, not guarantees of safety. It keeps particle filtration separate from gas/vapour protection, avoids product endorsements, and routes citizen pollution reports to Green Delhi, Sameer and DPCC rather than creating a parallel complaint database.
Medical education
Mechanism diagrams are teaching models, not anatomy claims
The education library covers PM size, lung deposition, AQI construction, exercise physiology, respirators and winter meteorology. Simplified diagrams are explicitly labelled as schematics; population-level associations are kept separate from individual diagnosis or prognosis.
Exposure uncertainty
A nearby monitor is not your lungs
A monitoring location describes ambient air around that point. Roadside exposure, indoor filtration, floor height, local construction and time spent in different places can all make personal exposure different from the displayed reading.
Primary references
CPCB / data.gov.in — Real time Air Quality Index from various locations ↗
Current-snapshot source. This official MoEFCC/CPCB high-value dataset is published through India's Open Government Data platform with hourly granularity and station-level pollutant fields.
CPCB — National Air Quality Index (real-time AQI portal) ↗
Official CPCB city/station AQI display. Delhi Air Health links to this as the authoritative AQI surface but does not scrape it into the app because a stable documented machine-readable endpoint has not been established for this project.
data.gov.in — Sameer (National Air Quality Index) ↗
Official OGD catalogue describing Sameer as an hourly AQI publication surface. The public resource currently does not expose a sourced webservice/API, so it is not used as an automated AQI feed.
Central Pollution Control Board (CPCB) ↗
Indian National AQI categories, official health-impact wording, particulate sub-index methodology and monitoring-network context.
Open-Meteo — ECMWF IFS weather model API ↗
Prospective meteorology covariates from a locked ECMWF IFS HRES 9 km model selection: temperature, humidity, precipitation, surface pressure, wind and planetary boundary-layer height. These are gridded model-derived values, not station observations.
ECMWF — Integrated Forecasting System (IFS) ↗
Underlying global numerical weather-prediction system for the v2.10 prospective meteorology layer. Model identity is versioned separately from air-monitor observations.
OpenAQ API v3 ↗
Secondary open-data source for monitoring-location metadata and hourly histories. In hybrid mode, an OpenAQ history series is used only after its station identity matches the CPCB OGD station.
CAQM — 2025 PM10 and PM2.5 concentration levels ↗
Primary annual particulate series. CAQM reproduces CPCB Delhi annual PM2.5 and PM10 values through 2025 and explicitly flags 2020 as COVID-affected.
CAQM Annual Report 2024-25 — Air Quality Perspective for Delhi ↗
Primary annual AQI comparison: average AQI plus counts of days with AQI at or below / above 200 for 2018-2024.
CAQM — 2024 Air Quality Perspective in Delhi ↗
Source table for monthly average Delhi AQI from 2018-2024. Delhi Air Health derives a simple cross-year monthly mean only to illustrate seasonality and labels that derivation explicitly.
CAQM — Why air pollution intensifies during winter in Delhi-NCR ↗
Primary meteorology source for the winter explainer: sustained emissions interact with regional transport, low wind, shallow mixing layers, fog/cold conditions and secondary aerosol formation; monsoon conditions provide dispersion and wet removal.
University of Delhi ↗
Institutional context for the DU expansion. Individual campus coordinates are stored with their own coordinate-source links in the campus registry.
OpenStreetMap ↗
Base-map tiles and geographic context for campus/monitor maps. Map attribution is shown directly on every map.
World Health Organization — Global Air Quality Guidelines ↗
Health-based pollutant guideline concentrations and broader health context. WHO guideline values are kept separate from AQI categories.
WHO — Air quality and health ↗
Medical explanation of particulate matter, cardiovascular, cerebrovascular and respiratory health effects.
US EPA — Particulate matter health effects ↗
Mechanistic and clinical background for educational explanations of fine-particle exposure.
CPCB — Broad guidelines for Public ↗
Official public-facing CPCB guidance for behaviour during poor air-quality conditions. Delhi Air Health keeps these statements separate from its own activity-specific interpretation.
US EPA — Frequent Questions about Particle Pollution ↗
Exercise-exposure mechanism: physical activity raises respiratory rate and minute ventilation, increasing inhaled particle dose; EPA also advises avoiding exercise near busy roads when particle pollution is unhealthy.
US EPA — Particle Pollution Exposure ↗
Mechanistic basis for the activity planner: higher minute ventilation increases inhaled air volume and can shift breathing from nasal toward oronasal routes, changing particle deposition.
AirNow — Particle pollution activity guidance ↗
General principle that prolonged or heavy exertion increases inhaled dose and may need modification when particle pollution is unhealthy. US AQI cut-offs are not transplanted directly onto Indian AQI values.
Delhi Environment Department — Green Delhi Application ↗
Primary Delhi citizen grievance route for pollution-related complaints. Delhi's Environment Department continues to list Green Delhi Application as an official service, and the Green War Room monitors complaints routed through the app.
CPCB — Guidelines for management of air-pollution complaints in Delhi-NCR ↗
Official complaint-routing guidance for Sameer, including photo/location evidence, complaint tracking and forwarding to the relevant implementing agency.
DPCC — Functions ↗
Current DPCC page listing the dedicated WhatsApp channel for picture/video complaints about leaf or garbage burning.
US EPA — Guide to Air Cleaners in the Home ↗
Indoor action guidance: source control, sensible ventilation, particle filtration, room sizing, CADR and the limits of portable air cleaners.
US EPA — What is a HEPA filter? ↗
Definition and performance context for HEPA particle filtration. Delhi Air Health keeps particle filtration separate from gas/vapour removal claims.
CDC/NIOSH — Community respirators and masks ↗
Respirator context: a well-fitted particulate respirator such as an N95 can reduce particle exposure, but it does not protect against gases or vapours.