Sensing the Air Quality

Venue for sensing the air quality and emissions program

In our home page, we mentioned that within product incubation, we were working on our own solution activities. The area of interest is within the internet of things (IoT) and is  targeted at low cost air pollution/air quality (AQ) solutions at this time. Thus we were pleased to participate in the 46th Intelligent sensing program, organised by the UK knowledge transfer network.

What were the main learnings from the event?

  • Big concerns on the level of small particulates, specifically PM2.5 and below.
  • EU AQ measurement standardisation is scoping “informative” sensing solutions.
  • Growing interest in AQ sensor networks.
  • UK government desire to leverage crowdsourced pollution data.
  • Key sensor criteria & findings from low cost sensing components.
  • Urban & journey pollution mapping.

Particulates

Can we meet the EU reduction targets for PM2.5 particulates by 2020? Should we be counting the number of particles rather than particle mass/m^3? Just one PM10 particle weighs as much as 1000 PM1 particles.

AQ sensor networks

Presentations from Alphasense and AirMonitors Ltd. pointed to the additional value coming from “lower than reference” quality sensors connected up as a network e.g. the ability to dis-aggregate pollution sources.

Crowdsourcing, sensor criteria and findings

The UK Environment Agency are looking to identify how they can better leverage crowdsource AQ data as a larger monitoring network than their existing 150 reference stations across the UK. However, the main concern is over the quality of this data. This then leads us to think about the air quality sensor and sensor system criteria:

  • Sensitivity: enough for the purpose e.g. movements within the general background outdoor AQ level
  • Specificity: responding to a specific gas pollutant and not being easily spoofed by the presence of other gases
  • Stability: the sensor performance remains predictable enough, compared to a reference over its intended lifespan

A couple of presentations mentioned using  low cost sensors based upon existing metal oxide technology – the learning here being that the sensor system stability is a challenging issue to manage. Mitigation seems so far to have been to adopt electrochemical type sensors but which can be significantly higher cost.

Hamamatsu was one supplier at the event claiming good individual gas detection capability using light absorption sensing e.g. a sensor set to the band gap of a specific gas. This looks an interesting avenue to explore further.

Overall, the sensor selection is one of the most significant factors for us to consider in our low cost AQ sensing solution.

Urban & air pollution monitoring from vehicles

A couple of interesting talks measuring pollution across journeys.

  • Motorway driving is quite bad for particulates exposure due to vehicle pollution “plumes”.
  • Air re-recirculation in cars provides quite some benefit to exposure levels, as long as the CO2 levels & humidity levels in the cabin don’t build up too much.
  • Urban NO2 hotspots experienced by cyclists on pathways, not only near road junctions but also when passing by industrial areas.
  • AQ pollution hotspots can move position dependent on the wind direction e.g. crossing over to the opposite side of the road. So, dynamic measurements or models are important.

 

 

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