Low-Cost Air Quality Sensors for Community Monitoring

Air pollution is a growing problem in both urban and rural areas. Cities face challenges like traffic, smoke from wildfires, and industrial activity, while rural areas deal with agricultural emissions, dust, and the same wildfire impact. Traditional reference stations measure air quality accurately but are costly and limited in coverage, making low-cost sensors (LCS) a more accessible alternative.

LCS can track indoor air quality, pinpoint pollution hotspots, or support outdoor studies. In this article, we’ll talk about how to best use LCS for community monitoring and research.

What Are Low-Cost Air Quality Sensors? 

Low-cost air quality sensors (LCS) measure different pollutants. These include particulate matter (PM), carbon dioxide (CO2), radon, ozone (O3), nitrogen dioxide (NO2), and volatile organic compounds (VOCs). They can also detect formaldehyde and environmental factors like temperature and humidity.

One of the most common uses for LCS is monitoring particulate matter (PM), which includes harmful particles like PM1, PM2.5, and PM10. These particles, often from sources like dust, smoke, and industrial emissions, are small enough to enter the lungs and bloodstream, causing serious health risks such as respiratory problems and cancer. They’re mostly used in situations where individuals suspect high PM levels due to smoke, dust, emissions, etc.

Unlike traditional reference instruments, which are larger, stationary, and highly accurate, LCS offers a more accessible and flexible alternative. They're easy to use, simple to set up, and can be quite accurate, depending on the manufacturer.

Their performance has proven effective in providing actionable insights for community monitoring and research.

Types of Low-Cost Sensors 

Low-cost air quality sensors come in three main types: stationary, mobile, and portable, each suited for specific applications.

Stationary Sensors

Stationary sensors are designed to remain fixed in one location and can be used for both indoor and outdoor air quality monitoring.

• Outdoor Monitors: Sensors like Purple Air are commonly used to monitor outdoor environments. They are ideal for tracking air quality trends in specific outdoor areas over time, such as neighborhoods or urban hotspots.
• Indoor Monitors: Devices like Atmocube are tailored for indoor spaces, such as schools, offices, and community areas, where they help measure pollutants in controlled environment.

Both types are easy to set up and often connect to networks or apps for real-time data access.

Mobile Sensors

Mobile sensors are typically mounted on vehicles, bikes, or drones to collect air quality data across larger areas. They are great for identifying pollution hotspots and monitoring variations during movement. However, mobile sensors may struggle with precision compared to stationary options. Their measurements can be influenced by rapid changes in environmental conditions, such as temperature, humidity, and wind, as well as the motion of the platform they are mounted on.

Portable Sensors

Portable sensors, like Atmotube PRO, are handheld devices designed for on-the-go air quality monitoring. They are compact, easy to use, and suitable for indoor and outdoor applications. Very few portable sensors connect to smartphones for real-time tracking and can last several days on a single charge.

Performance and Calibration of Low-Cost Sensors

Reference stations are very accurate because of their advanced equipment and adherence to strict regulatory standards for measuring air pollutants. However, they are expensive and need professional calibration and maintenance.

Low-cost air quality sensors (LCS) are cheap and easy to use, making them available to people and communities. Some models come pre-calibrated, while others may require user calibration or professional assistance. However, their accuracy can be affected by factors like particle size detection and humidity for PM sensors, and cross-sensitivity along with environmental conditions for VOC sensors. Despite these challenges, advancements like improved algorithms and lab-tested components make LCS more reliable.

To ensure reliability, it’s best to consult trusted third-party evaluations like those from AQ-SPEC (Air Quality Sensor Performance Evaluation Center), a program under the South Coast AQMD (Air Quality Management District). They provide objective performance reports to help users choose effective air quality monitors.

For example, according to AQ-SPEC’s tests, Atmotube PRO showed a high correlation between its PM1 and PM2.5 measurements and those of reference monitors.

Restrictions and Limitations of Low-Cost Sensors

Low-cost air quality sensors (LCS) are valuable tools for community-based air monitoring but come with some limitations. PM sensors rely on optical methods, like light scattering, to estimate particle concentrations, which can sometimes struggle with precise particle size differentiation and may be affected by humidity. Similarly, VOC sensors, which often use metal oxide (MOX) technology, provide total VOC (TVOC) readings rather than identifying specific compounds.  Environmental factors like temperature and humidity can influence their accuracy, too.

However, advancements in LCS technology are addressing these challenges. For example, here at ATMO®, we use lab-tested PM sensors with proven performance across major particle sizes and implement advanced normalization algorithms to minimize the impact of humidity and temperature. 

Application Opportunities

LCSs are essential for community-driven research, enabling individuals and groups to collect real-time data and advocate for environmental change. By identifying pollution sources and trends, communities can support local initiatives and present evidence to policymakers. This makes LCS a useful tool for raising awareness and supporting efforts to improve air quality.

Indoor Air Quality

Indoor spaces are often polluted due to poor ventilation, synthetic materials, cleaning products, and everyday activities like cooking. During events like wildfires, outdoor pollution can also seep indoors, worsening air quality. LCS allows researchers, NGOs, and communities to measure indoor air quality easily and affordably. 

For example, a Howard University study in Baltimore used Atmocube IAQ monitors to measure indoor pollutants like particulate matter (PM2.5), carbon dioxide, and formaldehyde. These findings highlighted the risks of indoor pollution and helped residents take practical steps to improve their air quality.

Outdoor Air Quality Monitoring

LCSs are equally valuable for monitoring outdoor air pollution, filling gaps left by traditional reference stations, which can’t cover all areas. Some key use cases of LCS for outdoor AQ monitoring include the following:

1. Identifying the cleanest routes for schools and commuters - LCS can help schoolchildren and commuters find the least polluted routes by tracking pollution levels along different paths. For example, in Barcelona, Spain, the ISGLOBAL institute used Atmotube PRO to track the effects of children's daily commutes on their health. The portable sensors collected GPS-linked air quality data to assess pollution exposure and intervention effectiveness.
2. Assessing exposure in sensitive locations (Schools, Hospitals, Workplaces) - It goes without saying how important it is to measure air quality and pollutants in places where sensitive people spend most of their time. LCSs can give localised data, so it’s easier to find tactics to avoid exposure.
3. Tracking wood burning in residential areas - Wood-burning stoves and fireplaces are a big source of particulate matter pollution. The spike is most visible in the cold winter months. LCS devices can raise awareness among communities on the pollution effects of wood-burning stoves and identify hotspots in their neighbourhood.
4. Early warning networks for wildfire smoke - Since LCS devices provide real-time data, they can warn people about the presence of smoke. As soon as air quality becomes hazardous, the device will note the change and notify the device owner.
5. Help with community monitoring projects - Unlike traditional air quality monitors, which can collect limited data, LCS can cover a broader area or serve as a supplement for more complete information.

Conclusion 

Low-cost air quality sensors are changing how we check and deal with pollution. They make it easier for communities and individuals to get involved. While they have limitations, advancements in technology are continuously improving their accuracy and reliability.

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If you're interested in learning more about how you can use ATMO's air quality monitors in your community research project, please reach out to us so we can answer all your questions regarding technical specifications, API access, and more.