Integrating particle counters into Smart Cities: real-time Air Quality Monitoring

According the the World Health Organization, particulate matter affects more people than any other pollutant and causes over 4 million premature deaths a year.

Sensors using the latest generation of laser particle counters immediately report levels of harmful particulates in the air at specific locations.

Particulate matter (PM) is categorised by size. PM1 is where particles are less than 1µm (0.001 mm), PM2.5 are bigger at ≤ 2.5µm (0.0025 mm) and PM10 larger still at ≤ 10 10µm (0.01 mm).

Particle sizes
Size distribution in micrometres (µm) of types of
airborne particles. Credit: Jisaac9 CC BY 3.0

Routine air quality measurements typically describe such PM concentrations in terms of micrograms per cubic meter (µg/m3). Sufficiently sensitive measurement sensors can count suspended particles in sizes of 0.3 µm and up. The sensor uses a complex algorithm to calculate the PM1, PM2.5 and PM10 mass concentrations.

How laser particle counters work

A laser produces a narrow beam of light in which all the light waves have very similar wavelengths and are in phase. This means that laser beams stay focused.

When particles pass through a laser beam they scatter the light. The sensor measures the light scattering to count the number and size of particles in the air. It can then immediately report the concentration of different sized particles.

Measuring pollution in Smart Cities over the Internet-of-Things

Air quality monitors using laser particle counters are being used by, for example, Urban Sensing Ltd to suppy real-time data about air pollution in smart cities. They typically mount the sensors on lamp posts around the city. In such systems pollution level data can be instantly reported along with vehicle counts, footfall, temperature, wind speed, humidity and other information. The small size and easy of installation means many monitoring points can be placed around the city - mapping air pollution black spots. This high spatial resolution allows targeted measures to raise air quality and improve peoples' health.

Particle counting in the smart city
Particle counter in use for air quality monitoring in the UK

Reference and Further Reading

Ambient (outdoor) air pollution, World Health Organization, 2018.

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