Citizen Air Quality Sensor Network

Pollutant

Controls

Wind speed 3.0 m/s

Emission rate 28 g/s

Sensor grid density 5 × 5

Network avg.

–

Peak reading

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Sensors in "unhealthy" range

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How it works

Real citizen networks (PurpleAir, AirVisual and similar) place low-cost optical sensors across a neighborhood instead of relying on a handful of official stations. This model reproduces the physics those sensors are measuring: a Gaussian plume spreading downwind from an emission source, exactly the textbook dispersion equation used by air-quality regulators.

C(x,y) = Q / (u·σy·√(2π)) · exp(−y² / (2σy²))
σy(x) = 0.32 · x^0.78

Q — emission rate at the source (higher = more pollutant released per second).
u — wind speed; faster wind stretches and dilutes the plume, slower wind lets concentration build up close to the source.
x, y — downwind distance and crosswind (lateral) offset from the source to a sensor.
σy — lateral spread of the plume, which grows with downwind distance.

Each pole in the grid is an independent low-cost sensor sampling the plume at its own position — exactly the hyperlocal, denser-than-official-network coverage that makes citizen air monitoring valuable for finding pollution hotspots a single central station would miss.

Good Moderate Unhealthy (sensitive) Unhealthy Very unhealthy

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