How to Determine the Accuracy of Air Quality Sensors?

According to a study, more than 8% of the total world diseases were caused by poor air quality in 2021, and since then, the number has been constantly increasing. So the first step in the preventative measures comes with the measurement of the air quality that we breathe in. The correct measurements of the air we breathe can be measured by an air environment integrated monitor, also commonly known as an air quality sensor.

Air quality sensors measure the quality of air we breathe. These are compact devices that can measure impurities or pollutants that are found in the air, such as carbon dioxide (CO₂), nitrogen dioxide (NO₂), carbon monoxide (CO), and particulate matter (PM2.5 and PM10). With these measurements, monitoring of air quality in homes, companies, industrial areas, and smart cities can be possible to get insights into the pollutants present in the environment and their concentration, so that preventative measures can be taken accordingly to improve breathing conditions, public health, environmental safety, and overall quality of life.

Installing air quality sensors and getting readings isn’t that simple. It all depends on how accurate or reliable the data the sensor can provide. The more accurate or reliable the data is, the more likely it is to implement pollution control strategies that can affect the overall city planning strategies, maintain workplace safety, and ensure that every member of the family breathes quality air. With the slightest inaccuracies in air quality readings, it can affect the overall policy making and decisions that can carry unnecessary health risks.

In this article, we will cover every factor that can affect the sensor accuracy, how they work, and the best practices to ensure that the air quality sensor keeps giving accurate results.

Understanding Air Quality Sensors

When it comes to air quality sensors, they come in different types that can measure several different parameters that can help to understand different air quality sensors suited for different monitoring needs and environments. Let’s take a look at different types of air quality sensors and the different parameters they can measure.

▪ Types of Air Quality Sensors

There are multiple types of air quality sensors made to suit the monitoring needs and the environment. Indoor sensors are typically made for indoor use, are compact in size, and focus on monitoring factors such as CO₂, VOCs (volatile organic compounds), and humidity to tell whether the indoor air quality is healthy to breathe in or not, so that precautionary or safety measures should be taken.

On the other hand, outdoor sensors are made to withstand harsher environmental conditions such as dust, wind, rain, and temperature fluctuations. They can also measure a wide range of pollutants like PM2.5, PM10, NO₂, and CO that can provide data that is vital for taking measures to improve urban air quality and providing insights to environmental agencies. The common design differences between the two sensors are weatherproof enclosures, enhanced durability, and advanced calibration systems.

▪ Parameters Measured by Air Quality Sensors

The parameters typically measured by air quality sensors provide insightful information to urban air quality networks and environmental agencies to track pollutants like particulate matter (PM2.5 and PM10) present in the air that have a direct impact on respiratory health and breathing-related problems. Air quality sensors can track harmful gases in the air, such as CO₂, CO, NO₂, SO₂, and O₃, which indicate emissions through combustion, traffic, or industrial emissions. Some of the advanced sensors are also capable of identifying VOCs, which are crucial in indoor sensors, suggesting the contamination of indoor air by excessive use of paints, cleaning agents, or furniture. Additionally, air quality sensors, especially the ones used in outdoor conditions, measure temperature and humidity to ensure that these factors are taken into consideration when the air quality readings are calculated to ensure accuracy.  

Importance of Sensor Accuracy in Air Quality Monitoring

Air quality couldn’t be improved if there are no readings or insight into how bad the air quality really is. So whether it's indoor environmental conditions or outdoor environmental conditions, having an accurate air quality sensor is crucial in monitoring air quality and taking measures according to the insights provided by the sensor.

With the readings provided by air quality sensors, governments and organizations can issue timely warnings and health alerts to reduce emissions and enforce pollution control policies that can help control the pollutants in the air. These sensors not only provide insights into air quality monitoring but are also great for individuals to make informed decisions, such as adjusting outdoor activities or adjusting ventilation to ensure a better quality of life.

Air quality monitoring is crucial, but if the sensor's readings are inaccurate, they can cause much bigger problems. With inaccurate readings, false alarms can be triggered, leading to wasted resources or unnecessary panic amongst people. Furthermore, if the pollution levels are under-reported, it may lead to people being exposed to harmful levels of pollution without any warning, which could be a bigger risk to people. In urban settings or industries, such accuracy in readings may lead to companies failing to comply with air quality regulations, posing a risk to people working in those conditions. In short, ensuring sensor accuracy is a key to making breathing conditions better for people and plays a key part in supporting cleaner environments and healthier communities worldwide.

Factors Influencing Sensor Accuracy

Multiple factors can directly or indirectly affect the sensor's accuracy in readings, and identifying those factors is crucial to make adjustments accordingly to ensure air quality sensors provide accurate readings. Let’s take a look at some of the common factors influencing sensor accuracy.

★ Environmental Conditions

Air quality sensors are highly sensitive, so that the readings can be affected by the changing environmental conditions, such as temperature, humidity, and interfering gases. Extreme temperatures, either too low or too high, can have a direct impact on the sensor’s response time. At the same time, changes in humidity factors can result in condensation or chemical reactions in the atmosphere that can deviate the readings from the actual values. Additionally, gases present in the surrounding environment near the sensors that are not targeted by the sensors can cause cross-sensitivity, resulting in inaccurate data.

★ Technology and Design

Not all sensors are built equally and may have differences in their technology and design. Some sensors are susceptible to providing stable and precise readings using advanced technology like NDIR for CO₂ or laser scattering for particulate matter. Some sensors feature a design that resists humidity and harsh weather conditions to provide stable and accurate readings, making them great for getting long-term, reliable readings across multiple air quality monitoring applications.

★ Maintenance and Calibration Needs

Over time, sensors drift from the actual calibrations based on the environment, aging, and environmental buildup. This is why regular calibration and maintenance are a necessity to ensure the readings are aligned with the actual conditions and reference standards. To ensure your air quality monitoring sensor keeps providing accurate results, always clean sensor inlets, verify the readings from the sensor against actual gas concentrations, and perform scheduled recalibration if you see the readings are drifting off from actual values to ensure dependable results for continuous air quality monitoring.

Methods to Assess Sensor Accuracy

There are multiple methods to assess sensor accuracy. We have identified some of the methods below to help you determine sensor accuracy and calibrate accordingly.

1. Laboratory Testing

One of the core methods of testing and verifying the accuracy of air quality monitoring sensors is laboratory testing. In a controlled environment, sensors are exposed to known quantities of pollutants such as CO₂, NO₂, CO, or PM2.5, and their readings are noted. Then the readings are compared with the original concentration of pollutants to check for deviations from standard values. Then adjustments are made accordingly before installations to ensure accurate results are provided. Laboratory testing is best for initial testing, as it is carried out in controlled environments, making it sufficient for calibrating indoor air quality sensors.

2. Field Comparisons and Co-Location

Unlike laboratory testing, which is carried out in controlled environments, field comparisons and co-location techniques are carried out in the actual environmental conditions. The field testing is crucial for outdoor air quality sensors to evaluate the sensor's consistency, correlation between the actual values from reference-grade monitoring stations that use high precision instruments, and the potential drift due to outdoor weather conditions such as variable weather and pollution conditions. With field testing, air quality monitoring sensors can be installed in outdoor conditions such as busy urban intersections, industrial areas, or quiet parks to assess the sensor's reliability across diverse environmental conditions. With the air quality sensor tested in real-world conditions, operational deployment and long-term accuracy can be achieved.

3. Data Analysis Techniques

The above 2 methods were related to testing, but the data analysis techniques use data to identify patterns and drift over time from the actual values in the sensor’s performance. Some of the standard statistical and analytical methods for air quality sensors include Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and correlation coefficients (R²). These techniques are used to calculate deviations from the actual mean or reference values. If you want to detect causal sensor drift or wish to track sudden anomalies, using time-series analysis could be a great option. With the data analysis techniques, scientists can create patterns that can help in future predictions of air quality and support timely recalibration for accurate results.  

Key Metrics for Evaluating Accuracy

• Mean Absolute Error (MAE):  MAE is a type of Absolute error metric that works by taking the average difference between sensor readings and reference values, providing a clear insight into the overall deviation from the mean value. MAE is less sensitive to outliers. The lower the MAE values, the better the accuracy and consistency in measurements of air quality monitoring sensors.

• Root Mean Square Error (RMSE): RMSE is also a type of Absolute Error metric that stresses larger deviations by squaring the errors before averaging, which makes it more sensitive to outliers. The lower the RMSE values, the better the accuracy and consistency in measurements of air quality sensors.

• Normalized Root Mean Square Error (nRMSE): nRMSE is a standardized way of comparing the accuracy of a sensor with other various pollution levels and environmental conditions. nRMSE is a way of expressing RMSE as a percentage of the mean reference value, explaining the relationship of error to an overall pollutant concentration value. Typically, an nRMSE below 10–20% is an acceptable range for high-quality sensors, ensuring results are reliable and reproducible across diverse environmental conditions.

Best Practices for Maintaining and Verifying Accuracy

To ensure consistent and accurate readings, calibrations, and maintenance are crucial. From time to time, verify the readings from the air quality sensor and compare them with the actual readings. If the readings are deviated, clean the sensor's inlet and filters to prevent dust accumulation that can cause hindrance in providing accurate readings. Ensure proper placement of air quality monitoring sensors during installations. Choose a place that is free from obstructions, direct heat sources, moisture, or obstructed airflow. Do follow manufacturer operational guidelines for recommended calibration intervals and environmental limits to enhance performance further. With consistent monitoring, timely calibration is a key to ensuring accuracy and precision in the readings.

Conclusion

Accurate air quality sensors play a key part in ensuring that the monitoring of air quality is exact once calibrated and installed in the right way. These sensors play a key part in protecting people from health and lung diseases caused by breathing polluted air by taking precautionary measures. On a government or commercial level, these sensors play a crucial part in implementing policies, guidelines, and solutions based on the readings provided by the sensors.

So if you are looking for an air quality monitoring sensor that provides dependable readings with precision and accuracy, Rika Sensor is a great option. They are known for offering sensors of high quality that are field-tested to ensure reliability and accurate results. Their range includes specialized options such as the RK300-03 CO₂ Transmitter, RK300-08 Multi-in-One Gas Sensor, and RK300-14 NO₂ Sensor, all designed to provide results that are accurate, reliable, and consistent. Do check out Rika’s complete line of air quality sensors at Rika’s official page to ensure every reading comes with confidence.