Air quality sensors for cities: what to measure and how to connect them
Outdoor air quality sensors help cities see pollution street by street. The challenge is turning many different sensor networks into one reliable picture.
What do air quality sensors measure?
- Particulate matter (PM2.5 and PM10): fine particles linked to traffic, heating and industry.
- Nitrogen dioxide (NO2): mainly from road traffic.
- Ozone (O3): formed in sunlight from other pollutants.
- Carbon monoxide and sulphur dioxide: from combustion.
- Carbon dioxide (CO2): mostly used indoors as a ventilation indicator.
- Temperature, humidity and wind: needed to interpret the readings.
Reference stations vs low-cost sensors
Reference monitoring stations are accurate but expensive, so cities have few of them. Networks of lower-cost sensors add density, showing differences between streets and neighbourhoods, but need calibration and quality checks against reference data.
How city air quality data is collected
- Sensors on lamp posts and buildings, often over LoRaWAN, NB-IoT or cellular.
- Vendor cloud platforms that expose REST APIs.
- Open data portals and OGC SensorThings services.
- Weather and atmospheric model data, in formats such as GRIB2 or NetCDF.
From many networks to one city view
- Connect every network and data feed, whatever its protocol.
- Validate readings and flag sensors that drift or go offline.
- Normalise pollutants, units and timestamps into one model.
- Combine air data with traffic, weather and city models in a digital twin.
What cities do with the data
- Public air quality maps and alerts.
- Traffic and low-emission zone planning.
- Health studies and measures around schools.
- Checking the impact of policies over time.
How ALLINLET helps
ALLINLET connects sensor networks, vendor APIs, open data and weather sources through one engine, so city teams get a single, consistent air quality stream instead of a collection of separate dashboards.
Frequently asked questions
How many air quality sensors does a city need?
It depends on its size and goals. Many cities combine a few reference stations with denser low-cost networks around schools, main roads and known hotspots.
Are low-cost air quality sensors accurate?
They are useful for trends and hotspots, especially when they are calibrated against reference stations and regularly checked for drift.
ALLINLET connects to IoT sensors and industrial systems through 900+ connectors across 22 domains, and delivers one clean data stream, in our cloud or in your own infrastructure.