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Sensor networks to monitor air pollution in cities

Sensor networks to monitor air pollution in cities

September 30th, 2010 - Alicia Asín, Manuel Calahorra

Studies show that more than 16,000 people die prematurely in Spain by breathing polluted air, being the traffic responsible for up to 80% of that pollution. This figure is 4 times greater than the number of annual traffic accident victims. In Europe, CO2 emissions from road transport (half of them come from urban transport) have increased by 32% since 1990. Each liter of fuel burnt is issuing up to 2.3 kg of CO2. Thus, each person who uses the car for journeys to work (with an average distance of approximately 15 km) emits about 2 tonnes of CO2 a year. The increase also generates more traffic jams, which cause a loss of 100,000€ million per year in the European Union. Monitor pollution levels in central cities is key to provide adequate information to citizens and take actions to reduce it.



On September 22nd, the "Day Without Cars" was celebrated as culmination of the European Mobility Week with a very low level of followers. One of the reasons for explaining the "failure" of the initiative is the lack of motivation, perhaps caused by the low level of information on the vehicle use impact. Curiously, pollution is one of the reasons that most degrade the quality of life in cities.



The following chart shows a ranking of european cities accordingly to environmental criteria. The complete study, that is UE funded, is available here.

Pollution monitoring and display to the citizens is essential to compare the impact of measures taken by municipalities and public institutions and raise public awareness. For example, monitoring of pollution in Stockholm city center made its citizens to approve in a referendum approve a congestion tax for accessing to downtown. The results were a 22% reduction in CO2 emissions and a 18% reduction in the average time of jams. Other cities such as London, Brisbane and Singapore have adopted similar measures.


The importance of these emissions is so high that even the air we breathe is regulated by the European Commission in the Directive 96/62 on air quality, which aims to ensure public health of citizens.


Waspmote along with the gases sensor board allows to monitor the following parameters to determine the quality of the air we breathe:

  • Nitrogen dioxide (NO2): it is a gas produced by the rapid oxidation of NO, which is produced by burning fossil fuels in vehicles and industry. It is a toxic and irritating gas that affects the respiratory system and also encourages the production of nitric acid (HNO3) responsible for acid rain.
  • Carbon dioxide (CO2): it is a gas naturally present in our atmosphere. Together with water vapor and other gases is one of the greenhouse gases that regulate Earth's temperature. Production in excess as a result of increased fossil fuel usage could have a direct impact on climate change.
  • Carbon monoxide (CO): it is produced in incomplete combustion, ie, when part of the fuel does not react completely due to a lack of oxygen. Its danger to humans and animals, once it sets in blood hemoglobin, it prevents oxygen transport, which can be lethal. Although in open space is easily diluted, the CO emission from the engines of cars in congested areas causes may have rates of 50-100ppm, which are dangerous.
  • Methane (CH4): it is produced when organic materia decomposes in oxygen-poor environments. As carbon dioxide, it is a greenhouse gas so its increase may contribute to global warming.
  • Hydrogen sulfide (H2S): it is emitted into the atmosphere by various industries, such as paper. It is particularly dangerous because it is a highly toxic gas and it is a sulfur dioxide precursor, one of the gases in the processes of formation of acid rain.In addition, this gas is specially annoying because of its foul smell.
  • Hydorcarbons (Ethanol, Propane, Butane, Isobutane, Toluene): they come from various sources, such as poor combustion of gasoline and diesel or indsutrial processes. They are, among others, responsible for greenhouse effect and contribute to produce respiratory problems.
  • Ozone (O3): it is a natural constituent that can be found at sea level with a concentration of 0.01 mg / kg. However, with intense solar radiation and high contamination coming from vehicles, its concentration can go up to 0.1 mg / kg being dangerous. In this proportion, the plants may be affected and human may experience irritation of nasal passages and throat and dryness in the lining of the respiratory tracts.

Monitoring air pollution with Waspmote is simple and cost effective due to it is features of wireless communication via the protocol 802.15.4 / Zigbee and battery power source, which make the deployment of a sensor network to operate for years easy and fast. Solar panels can recharge the batteries, ensuring a virtually perpetual operation. Finally, the GPRS module ensures data communication at all times while allows to sens SMS alerts according to defined thresholds.

Sensor networks deployed with Waspmote may consist of heterogeneous sensor motes, thus using the same network to monitor environmental pollution, as described above, ultraviolet radiation, park and garden irrigation management and even detect forest fires.


If you have any doubt about how to monitor the parameters mentioned in this article with Waspmote, do not hesitate to contact us asking for support.






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