Air pollution matters. No one likes bad smells but airborne particles can damage human health so it is important to know what is in the air we breath.

For Northamptonshire there is just one official site for measuring air pollution. This project complements official measurements with real-time outdoor, hyper-local readings using miniature air quality monitoring stations equipped with WiFi . Every few minutes the monitoring stations upload air quality data to a community website that shows estimated real-time air quality.

a monitor outside a primary schgool

Each station contains sensors measuring the amount of dust - technically particulate matter - in the outdoor air. The concentration of particulate matter [PM] is given in micrograms per cubic meter (µg/m³) ie the weight in one millionths of a gram of PM in a cubic metre of air.

The weight of two significant PM sizes in the airborne dust are estimated:
•  PM10   [particulate matter 10  microns and smaller]
•  PM2.5  [particulate matter 2.5  microns and smaller]

A micron, or micrometre, is one millionth of a metre so these dust sizes are invisible to the naked eye and explains why they need to be measured by electronic sensors.

PMs smaller than 2.5 microns can penetrate the lining of the lungs, enter the blood stream and be circulated round vital organs. As these can be the most hazardous to human health they need to be counted.

It is important to note that the measurements from these monitoring stations cannot be taken literally because their sensors are not calibrated to laboratory standards, nor are they operating under laboratory conditions. However their sensor components are identical, or broadly similar, to those used in professionally calibrated systems and they do provide an important indication of immediate pollution levels along with an archive of trends over time.