There is a growing worldwide concern over health issues presented by poor air quality, with the World Health Organisation stating that there are 4.2 million deaths each year resulting from exposure to ambient air pollution alone. Despite the recognised problem, the monitoring of air quality on a wider scale is still far from a resolved issue.
From an Irish perspective, air quality monitoring is largely in the domain of the EPA, with real-time monitoring stations currently in operation across only 17 of the Irish counties. This represents an interesting problem: air quality can vary wildly from one location to the next, yet the prohibitive costs and physical space requirements of monitoring stations make it difficult to record air quality data on wide scale, meaning that air pollution issues in areas lacking monitoring stations can go unnoticed.
Researchers in TSSG have proposed a possible solution as part of the recently published paper “Towards Wider Monitoring of Air Quality” for the 2018 European Transport Conference, held in Dublin. The paper describes an ambient air quality monitoring system which is highly-scalable and low-cost, using IoT technologies such as the Raspberry Pi, and a selection of connected gas sensors.
Image 1. Developed Prototype Sensor Unit
While traditional air quality monitoring instruments can cost hundreds or thousands of euros to measure a single pollutant, TSSG’s developed prototype totaled around €300 with the capability to measure 16 different air pollutants using several gas sensors, albeit with the caveat that most sensors were not pre-calibrated and did require a calibration process for accuracy reasons. The system collects and stores data, providing real-time feedback on the content of surrounding ambient air and its quality. The system is easily scalable, currently hosting nine environmental sensors for detecting the pollutants shown in the table below, with the capacity for up to seven more sensors to be added.
|Detectable Pollutants in Low-Cost Prototype Unit|
|Carbon Monoxide (CO)||Benzene|
|Sulphur Dioxide (SO2)||Ozone (O3)|
|Nitrogen Dioxide (NO2)||Liquefied Petroleum Gas (LPG)|
|Ammonia (NH4)||Carbon Dioxide (CO2)|
|Methane (CH4)||Oxygen (O2)|
|Particulate Matter (PM)||Relative Humidity|
Table 1. Air pollutants measured by prototype unit
The low cost and small size of each unit means that a wider networked monitoring operation would be more feasible, especially with a hybrid approach to air quality monitoring, combining existing stations with new, low-cost sensor node networks to service areas where large-scale monitoring operations are not physically or economically viable.
However, it must be noted that there are drawbacks to the low-cost monitoring approach. During the teams development and testing period, the primary deficiency was identified to be in accuracy levels. Low-cost sensors, while reasonably accurate, cannot achieve the same precision accuracy levels of professional-grade equipment, but this is offset by the fact that low-cost nodes can be more easily established throughout an area, generating larger volumes of localised data. This allows for air quality measurements to be taken on a micro-level, measuring data down to city block or street-level, which is not feasible when using traditional measuring instruments due to cost and space requirements.
The availability of micro-area data would then allow for air quality conditions to be considered in infrastructure planning or environmental initiatives, such as promoting green transport options where air quality is at its lowest.
The full research paper, “Towards Wider Monitoring of Air Quality”, was published for the 2018 European Transport Conference in Dublin, and is available for viewing on the AET website.