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Revealing the Invisible: Air quality sensor research in Ghana

In the coastal West African nation of Ghana, vital public health research is underway to unlock the potential of low-cost air quality monitoring. A team of passionate air quality scientists have created a localized air quality sensor evaluation facility in Accra, the nation’s bustling capital.

Afri-SET (The Sensor Evaluation and Training facility for West Africa) aims to evaluate air quality sensors and put them to work in West Africa (1). The sensor evaluation facility was inaugurated in Accra, Ghana by Dr. Allison F. Hughes, an atmospheric physics physicist from the University of Ghana, and Dr. Mike Giordano, the Executive Director of AfriqAir and is primarily funded by the Clean Air Fund (2).

“There's quite a data gap in Africa when it comes to data on air quality.” 

–Dr. Allison F. Hughes, University of Ghana

AfriqAir (Africa qualité de l’air) is a cross-continental network focused on evaluating low-cost sensors and reference grade monitors primarily in urban areas like Accra.

The facility came to fruition through a critical need for public health information. According to Dr. Hughes, “there's quite a data gap in Africa when it comes to data on air quality.”

IQAir contributed five air quality monitors to further air quality research.

But deploying low-cost sensors – the right low-cost sensors – is critical to filling in that gap. The project aims to evaluate more than 50 different sensor manufacturers over a three-year period. IQAir contributed five air quality monitors to further this research.

What is a sensor evaluation facility?

Sensor evaluation facilities measure local outdoor air quality with reference-grade monitors and low-cost at the same location. By collocating both reference-grade monitors with low-cost monitors, sensor evaluation facilities can best compare performance between the sensors.

Reference-grade monitors, while meeting high standards of data accuracy, are prohibitively expensive for wide-scale use. Low-cost air quality monitors make it possible to uncover poor air quality virtually anywhere, providing sorely needed data to both policymakers and affected communities – ideally, in real-time.

“Low-cost sensors are one of the main tools in the toolkit for air quality in the Global South.”

–Dr. Mike Giordano, Executive Director, AfriqAir

“Low-cost sensors are one of the main tools in the toolkit for air quality in the Global South,” explained Dr. Giordano.

The Afri-SET sensor evaluation facility in Accra, Ghana. Source: IQAir.

The Afri-SET sensor evaluation facility in Accra, Ghana. Source: IQAir.

Supplied low-cost sensors are being compared to reference-grade air quality monitor provided by the World Bank.

There are important science-driven reasons for the comparison.

“Low-cost sensors are sensitive to multiple factors that reference-grade monitors are not – such as ambient temperature, relative humidity, and even chemical properties of PM that vary with emission source. Low-cost gas sensors can even be sensitive to different pollutant gas mixing ratios,” said Dr. Giordano.

The effectiveness of low-cost sensors in accurately monitoring air quality is a topic of extensive research. Experts have found that the inherent sensitivities in these sensors, often seen as a limitation, can be significantly reduced through meticulous calibration and model development. The optimal method for enhancing the accuracy of low-cost sensors involves their collocation with reference-grade monitors. By placing these sensors alongside the more advanced, high-standard monitors, it becomes possible to fine-tune the low-cost sensors for better reliability and precision in diverse environmental conditions.

While sensor evaluation facilities exist in the U.S. and Europe, sub-Saharan Africa faces unique air quality challenges. A local understanding of pervasive air quality issues is needed to better understand the challenges.

As Dr. Hughes noted, low-cost sensors are in demand in Africa. “In most countries we don't have reference grade monitors, but we do have people – academia, and other citizen scientists and NGO's – who are interested in understanding the quality of air in African cities.”

air monitors

Sensor evaluation underway at Afri-SET. Source: IQAir.

Sources of air pollution in Africa

According to Dr. Hughes, Accra struggles with air pollution unique to its location. Air pollution sources include biomass being used for cooking and industrial activities, old, poorly maintained vehicles, dust from unpaved roads, and coastal sea salt.

During the dry season from November to March, desert winds – Harmattan winds – can sweep across the country from north to south, coating all surfaces in dust and sand (3).

There are also fires in the open grassland Sahel region just south of the Sahara and accompanying smoke (4).

But owing to a lack of air quality data, people breathing in air pollution are unable to know when or how to take action to protect themselves. Policy-makers are equally left in the dark without data to act on.

Given these specific environmental threats, Afri-SET and AfriqAir hope to better understand how low-cost sensors perform in these diverse environments. This has process has already started with a webinar introducing the basics of air quality modeling that was held in December 2023 (available to watch on YouTube) and an air quality certificate course jointly hosted by Afri-SET and Columbia University through U.S. Department of State funding (5).

Sensor deployment and progress to date.

The project began in September, 2023, and the evaluation process will span six months. After the evaluation period ends, contributed sensors will be deployed across the continent.

Among the low-cost monitors being evaluated are five AirVisual Outdoor air quality monitors. And while some of the monitors being evaluated in this project may be returned to manufacturers, the AirVisual Outdoor air quality monitors will remain deployed on the continent, continually providing free air quality data to communities.

Airvisual Outdoor

AirVisual Outdoor deployed on site. Source: IQAir.

The road ahead: Future goals and a commitment to open data

While the project is already underway, the researchers hope to extend its 3-year duration. They also intend to improve its reach by establishing similar centers in East Africa and possibly Central, and/or Southern Africa.

Afri-SET’s collected data will be provided on the organization’s site. The center embraces a philosophy of providing the world with free, open data – ensuring that air quality data is universally available to all people.

To be low-cost and effective, Afri-SET and IQAir agree that sensor data needs to be always free. If a manufacturer requires buyers to renew their license renewal for access to air quality data, that can be cost-prohibitive.

“We're even moving away from the term 'low-cost sensors’,” Dr. Hughes said. “Instead, we refer to them simply as 'air sensors,' recognizing that 'low-cost' is a relative term. What's considered low-cost in the global north might not be the same here in Africa.”

Building off the center’s experiences, Afri-SET and AfriqAir are committed to educating African communities on the importance of air quality. The organizations want to train students and citizen scientists to effectively deploy low-cost air quality sensors.

The takeaway

The complex, necessary work being carried out by Afri-SETI and AfriqAir aspires to address the data gap in air quality monitoring in Africa, promote open data sharing, and work towards policy changes to make it easier to use low-cost sensors. IQAir’s AirVisual Outdoor monitors will play a key role in helping realize the dream of globally accessible, local air quality information.

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