Ambient Air QualityAir quality refers to the state of the air we breathe and its composition in terms of pollutants present in the atmosphere. It is considered good when poll...
Read more Monitoring Stations (AAQMS) have become key infrastructures for monitoring and safeguarding public health in urban areas, industrial facilities and natural environments. They are an essential ally in addressing environmental risk situations. For instance, a report by Ecologistas en Acción reveals that, in 2024, almost two thirds of the Spanish population breathed air that exceeded the current legal pollution limits, highlighting the urgency of using accurate and up-to-date monitoring systems to protect public health.
Throughout this article, we analyse how the technological innovation of air quality monitoringControlling air quality is an essential task in order to enjoy optimal environmental conditions for healthy human development and to keep the environment i...
Read more stations, thanks to IoT-based sensors, has made them major environmental allies that are transforming air quality management. This enables authorities and management bodies to make immediate and precise decisions to reduce citizen exposure to air pollution.
What is an AAQMS?
An AAQMS is an advanced technological system equipped with sensors capable of detecting and quantifying critical air pollutantsAir pollution caused by atmospheric contaminants is one of the most critical and complex environmental problems we face today, both because of its global r...
Read more such as particulate matter (PM2.5 and PM10), gases like nitrogen dioxide (NO2)Nitrogen dioxide (NO2) is a harmful gas whose presence in the atmosphere is mainly due to the use of fossil fuels in combustion vehicles and industrial act...
Read more, sulphur dioxide (SO2)Sulphur dioxide (SO2) is a colourless gas with a pungent odour that causes an irritating sensation similar to shortness of breath. Its origin is anthropoge...
Read more, carbon monoxide (CO)The carbon monoxide (CO) is an invisible gas (colorless and odorless) that, at the same time, is a silent killer because in just a few minutes it exhibits ...
Read more, ozone (O3), volatile organic compounds (VOC)Volatile Organic Compounds (VOCs) are chemical substances primarily composed of carbon and hydrogen, but they can also contain other elements such as oxyge...
Read more, and other potential contaminants, as well as specific meteorological parameters (temperature, humidity, wind direction and speed, among others) that are relevant for an accurate analysis of the environmental situation. AAQMSs also form networks comprising multiple air quality monitoring stations strategically located at various measurement points.

AAQMS – Ambient Air Quality Monitoring Station
Main functions: real-time and continuous air quality monitoring
This air quality monitoring system generates environmental data continuously and in real time, providing an essential basis for risk assessment, public communication and the design of effective policies against air pollution.
AAQMSs represent the first line of defence against the effects of air pollution, a persistent challenge to global health.
Their technological evolution and growing integration into public strategies are key to advancing towards cleaner, safer and healthier urban environments, committed to ensuring compliance with environmental regulations.
Acronyms and associated terms
In the field of sensor-based air quality monitoring, there are multiple concepts (identified by acronyms) used to define the systems, technologies and methodologies employed. Understanding the difference between AQS, AAQMS, CAAQMS and other related terms allows us to better comprehend the functionality, capabilities and applications of the systems used to assess air pollution, thereby protecting public health and the environment.
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The main terms associated with air quality monitoring systems are based on:
AQS (Air Quality Standards) vs. AQMS (Air Quality Monitoring Systems)
AQS is a generic term used to refer to a sensor or a basic set of sensors for detecting specific air quality parameters in a given location or enclosed space. In contrast, an AQMS is a more complex and comprehensive system that integrates multiple AQS sensors as well as advanced technologies designed to measure and process multiple parameters and generate alerts on air quality in real time and on a continuous basis. AQMS systems are typically installed in fixed or mobile monitoring stations in outdoor or industrial environments, helping to comply with environmental regulations and protect public health.

Instruments for the measurement of different air pollutants mounted in an open rack
CAAQMS (Continuous Ambient Air Quality Monitoring Systems) / CAQM
CAAQMS, or continuous ambient air quality monitoring systems, represent a further step in the advanced technological evolution within the field of environmental air quality assessment. These systems enable the continuous and automatic measurement of critical air quality parameters in real time, thanks to the integration of electronic sensors and IoT technologies.
CAAQMSs capture data uninterruptedly, transmitting information to centralised digital platforms that facilitate immediate analysis, storage and accessible visualisation for both authorities and the general public. They are essential in high-density population areas or industries, where it is crucial to have automatic alerts to avoid exceeding legal limits or to protect public health by deploying immediate responses to critical air quality episodes.
The acronym CAQM (continuous air quality system or process) generally refers to the continuous monitoring of air quality, a concept closely related to CAAQMS. In some sources, these terms are used interchangeably, emphasising that the main focus lies in the permanent and reliable capture of data on pollutant parameters to generate long-term information for identifying trends and facilitating early environmental decision-making in line with regulatory standards.
Sensor-based systems for ambient air quality monitoring
Currently, air quality monitoring benefits from the remarkable development of electrochemical, optical and fluorescence sensors, among others, as they enable precise and efficient detection of pollutants. These sensor-based systems are characterised by their ability to provide real-time data, be scalable and adapt to various applications, from urban monitoring to industrial or rural environments. Furthermore, integration with wireless communication technologies and digital platforms enhances the analysis and intelligent environmental management they provide, facilitating the implementation of proactive policies for the control and mitigation of air pollution.
Portable monitoring stations vs. fixed AAQMS
Portable monitoring stations are compact and mobile devices designed to assess air quality in different locations and contexts, enabling spot measurements or temporary campaigns. Their main advantage lies in the flexibility and speed to identify pollution sources or validate data from fixed stations.
In contrast, fixed AAQMSs are permanently installed systems in strategic locations, capable of conducting continuous or semi-continuous detailed assessments of air quality in a given area. While fixed stations usually feature more robust and higher-precision technology, portable stations complement the monitoring network by facilitating the spatial and temporal diagnosis of air quality.
Main differences between systems
In the field of environmental monitoring, it is essential to understand the differences between the various systems and technologies available for air quality monitoring. From air quality monitoring platforms to portable air quality stationsAir quality stations are systems dedicated to monitoring atmospheric pollution, essential for measuring the concentration of pollutants in a specific area....
Read more, each option offers specific features tailored to different environmental control needs.
Continuous monitoring vs. periodic monitoring
Continuous monitoring is based on the uninterrupted and real-time collection of environmental data through automated systems, such as those integrated into modern air quality monitoring platforms. This enables the immediate detection of any change in pollutant concentrations, facilitating rapid responses and detailed analysis of atmospheric behaviour.
On the other hand, periodic monitoring involves taking samples or measurements at defined intervals, which may be daily, weekly or monthly. It is usually carried out using portable air quality stations or manual samplers. This methodology is useful for spot assessments or when financial resources are limited, although it does not offer the same continuity and temporal accuracy as continuous monitoring.

Evaluation carried out by the US EPA of different Air Quality Sensor Systems (AQMS)
Reference instruments vs. low-cost IoT sensors
Reference instruments are highly accurate and calibrated devices, traditionally used in fixed stations within AAQMS networks. These devices comply with international standards to certify data validity, which is crucial for regulatory studies or rigorous air quality analyses.
In contrast, low-cost IoT sensors represent a technological revolution, enabling the massive and decentralised expansion of environmental monitoring. Although their accuracy and stability may be lower compared to reference instruments, these sensors offer advantages such as portability, ease of installation, and the ability to integrate into digital platforms to obtain real-time data from multiple locations.
Interconnected AAQMS network vs. standalone units
An AAQMS network consists of stations and sensors strategically distributed, all interconnected via digital platforms that allow for the integration, analysis and joint visualisation of data. This facilitates the identification of spatial and temporal patterns of pollution, as well as the coordinated management of environmental alerts and public policies.
By contrast, standalone units operate independently, without direct communication with other stations or central systems. While they can be useful for specific monitoring or in remote areas, their ability to provide a global and real-time overview of air quality is limited, restricting their effectiveness in comprehensive environmental management.
Summary Table
System | Features |
---|---|
AQS (Air Quality SensorMeasuring air quality is essential for improving human and environmental health. Changes in the natural composition of the air we breathe are common in ind... Read more) |
A sensor or basic set of sensors for detecting specific air quality parameters in a given location, generally in enclosed spaces or for targeted applications. |
AQMS (Air Quality Monitoring System) | General air quality monitoring system that integrates multiple sensors and technologies to measure, process and display data on pollutants. It can be fixed or mobile, and is used in indoor, outdoor or industrial environments. |
AAQMS (Ambient Air Quality Monitoring System) | A specific type of AQMS designed to monitor outdoor ambient air quality. It complies with official standards and is used to assess pollution in large urban or rural areas. |
CAAQMS (Continuous Ambient Air Quality Monitoring System) / CAQM | Advanced systems that enable continuous and automatic measurement of critical air quality parameters in real time, integrating electronic sensors and IoT technologies. They are essential in densely populated or industrial areas. |
Reference instruments | Highly accurate and calibrated equipment, traditionally used in fixed stations. They comply with international standards and are crucial for regulatory studies. |
Low-cost IoT sensors | Portable and affordable sensors that enable the large-scale expansion of environmental monitoring. They provide real-time data, although with less accuracy than reference instruments. |
Interconnected AAQMS network | Network of stations and sensors distributed and connected via digital platforms, enabling joint analysis and coordinated management of alerts and public policies. |
Standalone units | Stations or sensors that operate independently, useful for specific monitoring or in remote areas, but with limited capacity to provide a global and real-time overview. |
Portable monitoring stations | Compact and mobile devices for spot measurements or temporary campaigns. They offer flexibility and speed in identifying pollution sources. |
Fixed AAQMS | Permanently installed systems in strategic locations, with robust and precise technology for continuous or semi-continuous air quality assessments. |
Basic components of an AAQMS
An AAQMS network or monitoring system is composed of several essential elements that enable the measurement, transmission and analysis of data on atmospheric pollutants to assess and control air quality. Among its fundamental components are its sensors, data acquisition and transmission systems, the rigorous calibration processes they undergo, and the maintenance they require, all integrated through specialised digital platforms.
Gas and Particle Sensors (PM, NO2, O3, CO2)
Sensors are the heart of an AAQMS, as they are responsible for detecting and measuring the main atmospheric pollutants. The most common include:
- Particle sensors (PM2.5, PM10): use optical or gravimetric technologies to detect particulate matter in suspension; essential for assessing air pollution caused by dust and aerosols.
- Gas sensors: measure key pollutants such as nitrogen dioxide (NO2), ozone (O3), carbon monoxide (CO), and carbon dioxide (CO2)Carbon dioxide (CO2) is a gas that occurs naturally in the atmosphere and plays a crucial role in the life processes of the planet. This gas, also known as...
Read more using electrochemical, chemical or infrared techniques, enabling precise readings of their concentrations.
These sensors must be strategically located to capture representative ambient air data, and their operation must ensure sensitivity and stability to identify changes in pollution levels.
Data acquisition, transmission and platform integration
The information collected by air quality sensors is gathered and transmitted continuously via a data acquisition system (DAS). This system organises and validates the data, which is transmitted through wired or wireless networks to digital platforms dedicated to environmental management.
These platforms enable storage, processing and analysis in real time, facilitating the visualisation of trends, the generation of automatic alerts and the integration of data for informed decision-making by authorities and environmental managers. Digital integration makes it possible to monitor air quality status from any location, improving rapid response capability.
Calibration, QA/QC and routine maintenance
Sensor calibration in AAQMS is crucial to ensure the accuracy and reliability of the data. It involves adjusting the sensors using certified references to correct deviations that may arise from wear, environmental conditions or equipment ageing.
Quality assurance (QA) and quality control (QC) processes include periodic reviews, comparison with reference methods and validation of results. In addition, routine maintenance includes cleaning, replacement of worn components, and continuous system checks to prevent failures or erroneous data.
Sensor calibration in Kunak AAQMS is carried out through a rigorous process that guarantees accurate and reliable data. Kunak AIR Pro sensors, for example, are factory pre-calibrated to ensure the best possible accuracy at the time of initial deployment. However, to optimise sensor performance, a final local calibration is usually required once installed at the definitive location.
For Kunak equipment, the technical procedure includes:
- An initial stabilisation period of 2 days prior to calibration.
- Two-point calibration: zero and span, comparing measurements with those from a reference station.
- Calibration and adjustments are performed using Kunak’s specific calibration tool, with no need for post-processing as the correction is calculated directly on the device.
- The collected data are averaged and correlated with the reference station for validation.
- Calibration is maintained throughout the monitoring period unless a specific recalibration is indicated.
- Data quality is validated only when a valid reference is available for comparison.
These practices ensure that the AAQMS operates at optimal performance, meeting international standards and environmental regulations, which is essential for effective air quality management.
Applications and deployment scenarios
The installation of AAQMS and the continuous monitoring of ambient air are fundamental pillars for the effective management of air quality in various environments. Depending on the objective and location, ambient air quality monitoring systems are adapted to provide accurate and timely data that support decision-making, environmental protection and public health.
Urban air quality networks
Urban monitoring networks are established through the strategic installation of multiple AAQMS stations distributed across metropolitan areas, enabling continuous real-time monitoring of ambient air. These networks facilitate the tracking of pollutants generated by vehicular traffic, commercial activities and diffuse sources, also helping to identify areas with higher concentrations of pollutants.
In addition, the collection of integrated data on digital platforms supports the creation of detailed air quality maps, early warnings for vulnerable populations and the design of urban policies that promote environmental improvement and collective health.
Industrial emissions monitoring
The installation of AAQMS in industrial areas is aimed at the continuous monitoring of ambient air around industrial facilities and factories to control the emission of specific pollutants. These systems detect real-time variations in compounds such as NO2, SO₂, volatile organic compounds and particulate matter, enabling industries to adjust their processes and comply with the limits set by environmental regulations.
Constant monitoring is also vital to minimise environmental impacts, prevent acute pollution episodes and maintain transparency in environmental management with the community and regulatory authorities.
Research and regulatory compliance stations
Stations dedicated to research and regulatory control represent a specialised use of AAQMS installation, where data accuracy and reliability are priorities. In these scenarios, continuous ambient air monitoring is accompanied by strict calibration protocols, QA/QC and maintenance to ensure the scientific and legal validity of the measurements.
These stations support studies on the temporal evolution of pollutants, evaluation of public policies and verification of regulatory compliance in different regions or specific areas. Their contribution is essential to underpin technical, legal and environmental decisions for the benefit of air quality and public health.
Top 5 FAQs about AAQMS
How does an AAQMS differ from an AQMS?
An AQMS (air quality monitoring system) is a general air quality monitoring system that can be implemented in different environments (indoor, industrial, mobile) and includes AQS sensors as well as technologies to collect, process and display data on airborne pollutants.
In contrast, an AAQMS (ambient air quality monitoring system) is a specific type of AQMS designed exclusively to monitor outdoor ambient (environmental or atmospheric) air quality. It focuses on collecting data on pollutants affecting large urban or rural areas and usually complies with official standards and methodologies defined by regulatory agencies such as the US EPA or the WHO (World Health Organization).
How do sensor-based AAQMS compare to reference monitors?
While reference monitors are the standard for regulated measurements due to their certified accuracy and reliability, sensor-based AAQMS, although less precise, allow for wider coverage at a lower cost, making them ideal for detecting trends, conducting urban mapping or supporting immediate decision-making.
What are the essential components of an AAQMS?
An AAQMS (ambient air quality monitoring system) is designed to assess ambient air quality through a series of interconnected and specialised elements:
Gas and particle sensors that must be stable and strategically located to accurately represent ambient air conditions:
- Particle sensors (PM2.5 and PM10):
Use optical or gravimetric technologies to detect and quantify suspended particles that affect health and environmental visibility. - Gas sensors (NO2, O3, CO, CO2):
Employ electrochemical, chemical or infrared techniques to measure the concentration of key gaseous pollutants.
They must also have data acquisition and transmission systems (DAS) that:
- Collect real-time data from the sensors.
- Validate and structure the collected information.
- Transmit the data via wired or wireless networks to digital platforms.
The digital integration of this data into environmental platforms serves to:
- Store and process data.
- Real-time analysis.
- Visualise trends and generate automatic alerts.
- Provide remote access for decision-making by authorities or environmental managers.
How often should AAQMS be calibrated and maintained?
The calibration frequency of AAQMS networks depends on several factors such as sensor type, environmental conditions, intensity of use and regulatory requirements. Nevertheless, there are general best practices:
Calibration
- Initial: At the time of installation, a local calibration is recommended even if the sensor is factory pre-calibrated.
- Periodic:
- Every 6 to 12 months for electrochemical, optical or infrared sensors, depending on the manufacturer and operating environment.
- Monthly or quarterly in critical environments or those with high environmental variability.
- Special events:
- After significant changes in location, weather conditions or following major maintenance.
- If data deviations or error alerts are detected.
QA/QC (Quality Assurance and Quality Control)
- Intermediate checks:
- Monthly or bimonthly, comparing with reference monitors or certified standards.
- Participation in intercomparison programmes or proficiency tests to validate metrological traceability.
- Internal audits:
- Annually, to review procedures, records and system performance.
Maintenance
- Preventive:
- Monthly: Sensor cleaning, connection checks, power supply verification.
- Quarterly: Filter replacement, inspection of electronic components, firmware updates.
- Corrective: As required, in the event of failures, reading errors or performance degradation.
- Documentation: All maintenance must be recorded in a master validation plan (MVP) or technical logbook.
What platform functionalities are critical in an air quality monitoring platform?
An effective platform should integrate hardware, software and environmental analytics to deliver useful, accurate and actionable data. These are the most critical functionalities:
Data visualisation and analysis
- Real-time dashboards with intuitive graphs of pollutants (PM2.5, PM10, NO2, O3, CO, SO₂, etc.).
- Interactive maps with geolocation of stations and nodes.
- Historical data and trends for temporal analysis (hourly, daily, monthly).
- Predictive models to anticipate pollution episodes.
Alerts and notifications
- Automatic alerts when critical pollution thresholds are exceeded.
- Notifications for authorities, managers or the public.
- Customisable alert settings according to local regulations or specific needs.
Integration and connectivity
- Compatibility with multi-sensor stations and sensors (gases, particles, meteorology).
- Wireless connectivity for continuous data transmission.
- Integration with Smart City or BMS (Building Management Systems).
Device management
- Device status (battery, connection, calibration).
- Remote OTA (Over-The-Air) configuration for adjustments and resets.
- Grouping and classification of nodes by zones, organisations or projects.
Data export and publication
- Download of historical data in CSV or API formats for external analysis.
- Web widgets to display data on public or institutional websites.
- Publication as an official station in collaborative or governmental networks.
Security and traceability
- Role-based access control (administrator, technician, observer).
- Audit log for changes in configuration or calibration.
- Data validation through QA/QC and comparison with reference monitors.
Conclusion
The implementation of an AAQMS network that combines advanced sensors and a robust platform for continuous ambient air monitoring represents a significant step forward in the effective management of air quality. The key differences between systems (such as continuous or periodic monitoring, the use of reference instruments versus low-cost IoT sensors, and integration into interconnected networks versus standalone units) highlight the importance of choosing the right technologies according to the application scenario.
The deployment of advanced technological sensors, rigorously calibrated and maintained, integrated into digital platforms capable of acquiring, transmitting and analysing data in real time, enables agile, precise and reliable environmental monitoring. This not only facilitates early detection of pollutants and detailed assessment of atmospheric conditions, but also expands the capacity for evidence-based administrative, regulatory and operational decision-making.
Therefore, opting for an interconnected and technologically advanced AAQMS network not only optimises the quality and coverage of monitoring, but also strengthens the protection of public health and the environment through proactive environmental management based on real-time data. Ultimately, modernised AAQMS networks are essential to address current and future challenges in air pollution control.