Sensing Air Pollution

Our Air-quality case study is based on three main components:

  • a SensorBox;
  • a smartphone with the free app AirProbe;
  • a dedicated Web server and Web applications;

The SensorBox is a portable device that measures concentrations of pollutants in the air and localize them through a GPS. This is done one time per second in order to have a detailed map of the pollution while you walk around. Using a smartphone with AirProbe it is possible to see the measurement in real time using a Bluetooth connection with the SensorBox. Moreover using an Internet connection, AirProbe sends all the measurements to the EveryAware server that collects in real time data from all users. Through dedicated Web Applications users can access the ensemble of the data gathered by the community of users along as personalized information concerning personal levels of exposure to pollutants.

Sensor Box

Our SensorBox is a small measuring system which use different low-cost gas sensors to evaluate air pollution. It is small enough to be carried around in a backpack and is powered with an external battery.

SensorBox has a small fan that pushes external air into a chamber where there are different sensors that measure air pollutants. In order to realize a small and cheap device we used a series of low-cost gas sensors. These perform well in highly controlled environments like a lab while in real-life conditions their performance and accuracy are affected by a series of factors like wind, weather condition or interfering gases. So it is very difficult to give a precise and reliable reading of a pollutant's concentration with individual sensors. The main challenge of our SensorBox is whether the coupling of several different low-cost sensors helps in reducing disturbances and provide with a sufficiently accurate measurements. Our SensorBox is calibrated against certified instruments detecting ultrafine particle (UFP) and Black Carbon, the goal being that of providing reliable observables to quantify air pollution even without individually accurate gas sensors

Application purposes

AirProbe allows the user to monitor Air Pollution and enrich the readings with personal annotations. It represents the interface between the SensorBox and the main server and it is primarily designed to:

  • display information about the current air quality;
  • record the user trip: Air Probe receives geo-referenced data collected in real time from sensor box and shows them on a map;
  • let the user to annotate his journey: every user action is done in a simple and quick way. Actions as opening the Bluetooth connection, recording a trip and seeing it on a map, inserting a personal annotation are easily performed in a few steps.

A track is the journey that one person takes and is created when the user turns on the SensorBox and ends when the SensorBox is switched off. In this time-lag, the connection between the sensor box and the smartphone is active.

Application general structure & display modes

AirProbe is composed by different views, associated to different functionalities, and organized in "tabs":

  • Map: There are two modes: user track map mode and community map mode; in user track map mode, the app shows the track corresponding to the geo-referenced measures received in real time from the SensorBox; in community map mode, the app shows only the subjective annotations made by the community of users around the current position;
  • Graph: a real time graphs shows the current values, received from the SensorBox of the 8 pollutant sensors;
  • Share: it lets the user to log in on Facebook and Twitter (to share geo-referenced annotations and pollutants data);
  • Sensor box: it shows helpful information on the status of Bluetooth connection, technical data about sensors as well as the GPS status.
    The app needs an Internet connection to send data to the server and to display them on Google Maps. To avoid loss of data, it uses a store'n'forward mechanism that allows to store locally data when Internet connection is not available and send them to the server when the connection becomes active again.

Air probe adapts to different "user profiles"

The functionalities and interaction modes of Air Probe are studied to let different types of users to use the application in a simple way. For example, if you are a cyclist, the minimalist and simple interface quickly let you to check the current air quality, to insert annotations (limited text entry), record trips and send the info to the server for offline analysis via a web application. If you are a mum, and every day you repeat the same journey to walk your children to or from school, you must only switch on Air Probe and forget it in your bag. Get it from your bag only if you decide to annotate what you noticed during the journey, or to check the level of exposure at every time!

In the same way, if you are a commuter, you can record your everyday track to collect a denser set of reading in an aggregated area and, if you go to work using public transport, you have time to annotated you experience.

Different types of user can benefit from using this application: runners, pedestrians, tourists, and so on...


The picture above shows an example of measurement performed in Turin. The yellow trace represents the output of a CO sensor. The highest value of gas concentration were measured along the main road, highlighted in red, especially at the intersections. The green area, instead, is a pedestrian area where the gas level is clearly lower. Below you can see other examples of traces for different gases.


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