What is an Air Quality Sensor

An air quality sensor, or comprehensive air monitoring device, is designed to measure real-time pollutant levels and environmental conditions in the atmosphere. Air quality monitoring is an important part of protecting the environment and managing public health. It is mainly used in indoor and outdoor environmental monitoring, air purification equipment, fresh air systems, industrial exhaust emissions, occupational safety assessments, and other fields.

Contents

1. Common Monitoring Parameters for Air Quality Sensors
2. Types and Principles of Air Quality Sensors
3. Application Areas of Air Quality Sensors

Common Monitoring Parameters for Air Quality Sensors

In practical applications, air quality sensors mainly monitor the following key parameters:

• Particulate matter (PM2.5 and PM10): Reflects the concentration of particulate matter in the air, with primary sources including industrial emissions, vehicle exhaust, coal combustion, dust, and biomass burning. PM2.5 (particles with a diameter of ≤2.5 micrometers) can directly enter the alveoli, triggering inflammatory responses and affecting the function of organs throughout the body.
• Carbon dioxide (CO2): Indicates the freshness of the air. Short-term exposure to high concentrations of CO2 can cause oxygen deprivation, headaches, or even unconsciousness; long-term inhalation of elevated CO2 levels may lead to chronic respiratory and cardiovascular diseases.
• Volatile organic compounds (VOCs): Some VOCs are harmful to human health, so their concentrations must be monitored. Components such as benzene and formaldehyde have been classified as Group 1 carcinogens by the World Health Organization.

In addition, environmental factors such as temperature, humidity, and oxygen levels can also be monitored by air quality sensors. For example, by monitoring temperature, humidity, and VOCs, it is possible to detect environmental conditions conducive to mold growth and issue mold risk warnings.The above monitoring parameters not only reflect the main sources of air pollution, but are also closely related to human health.

Types and Principles of Air Quality Sensors

As environmental pollution issues become increasingly prominent and public health awareness continues to rise, air quality sensors with their diverse detection principles and technical characteristics have established a comprehensive environmental monitoring network across various applications, including industrial emissions monitoring, indoor air quality control, smart city management, and personal health protection. Based on monitoring objectives and operational principles, sensors can be categorized into two main types:

Classification by Monitoring Objective

Particulate matter sensors
Particulate matter sensors are primarily used to detect suspended particles in the air, such as PM2.5 and PM10. These sensors typically employ laser scattering, beta ray absorption, or gravimetric methods to measure particle concentration. Particulate matter sensors calculate concentration by analyzing the intensity of scattered light from particles, offering real-time performance but requiring regular cleaning of optical components to maintain accuracy. Beta ray absorption methods are commonly used in environmental monitoring stations, offering higher precision but at a higher cost. The gravimetric method involves collecting particulate matter on a filter membrane and calculating concentration through weighing, yielding accurate results but unable to provide real-time monitoring.

Gas sensors
Gas sensors are used to detect specific pollutants in the air, primarily including:

• VOC (volatile organic compounds) sensors: Detect harmful gases such as formaldehyde and benzene, commonly using semiconductor or electrochemical principles. Semiconductor sensors are based on changes in the resistance of metal oxide materials, while electrochemical sensors generate current signals through oxidation-reduction reactions.
• CO2 sensors: Mostly use NDIR (non-dispersive infrared) technology, which measures CO₂ absorption of specific infrared wavelengths to calculate concentration.
• Toxic gas sensors: These sensors detect gases such as CO, NO₂, and SO₂, and typically use electrochemical sensors, which are highly sensitive but have a relatively short lifespan.

Temperature and humidity sensors
Although temperature and humidity sensors do not directly detect pollutants, they play an important supporting role in air quality assessment. These types of air quality sensors typically measure environmental temperature and humidity based on capacitive or resistive principles, and commonly include integrated sensors with digital outputs. Temperature and humidity data can be used to correct readings from other gas sensors, thereby improving overall monitoring accuracy.

Classification by Working Principle

Electrochemical sensors
These sensors generate a current signal through redox reactions between the target gas and the working electrode. They offer the advantages of good selectivity and high sensitivity, but their service life is limited by electrolyte consumption.

Semiconductor sensors
These sensors utilize the principle of resistance changes in metal oxide semiconductor materials caused by gas adsorption. They are cost-effective but susceptible to environmental temperature and humidity, requiring regular calibration.

Infrared sensors (NDIR)
These sensors measure gas concentration by calculating changes in transmitted light intensity based on the characteristic absorption of different gas molecules at specific infrared wavelengths. They offer good stability but have complex optical system structures.

Laser scattering sensor
Measures particle concentration by detecting the intensity of scattered light from particles interacting with a laser beam. Enables real-time continuous monitoring but requires high cleanliness of optical components.

Photoionization detector (PID)
Utilizes high-energy ultraviolet light to ionize gas molecules and measures concentration by detecting ion current. Exhibits extremely high sensitivity for VOC detection but has high equipment costs.

Additionally, there is a multi-functional composite sensor that integrates PM2.5, CO₂, VOC, and temperature/humidity measurements into a single unit, enabling comprehensive monitoring of air quality. This air quality sensor features a modular design that seamlessly combines multiple sensing technologies. Through intelligent algorithms, it performs fusion analysis on data from various parameters, significantly enhancing monitoring efficiency while providing a more accurate representation of overall air quality conditions. Its compact structure makes it particularly suitable for smart homes, office environments, and other spaces with limited space, providing users with a one-stop air quality monitoring solution. At the same time, multi-parameter collaborative monitoring can help identify the correlation between different pollutants, providing data support for precise environmental control.

Application Areas of Air Quality Sensors

In various air quality monitoring application scenarios, choosing the right sensor is crucial. Different environmental requirements, monitoring objectives, and budget constraints determine the type of sensor technology we need to use. ATO industrial automation systematically summarizes the typical application characteristics of air quality sensors in different fields to help you make informed decisions based on your actual needs. Whether you require high-precision environmental monitoring stations or cost-effective smart home devices, understanding the performance characteristics and application compatibility of various sensors can make your air quality monitoring solutions more precise and efficient.

Environmental Monitoring and Weather Forecasting

Air quality sensors play a critical role in environmental monitoring stations and meteorological observation systems. Environmental protection departments utilize high-precision sensor networks to monitor urban air quality index (AQI) in real-time, providing data support for pollution warnings and governance decisions. Meteorological stations use sensor data to study the dispersion patterns of atmospheric pollutants, enhancing the accuracy of weather forecasts. In particular, laser scattering PM2.5 sensors and NDIR CO₂ sensors, renowned for their stability and reliability, are widely deployed in national-level environmental monitoring networks.

Industrial Safety

In industrial fields such as petrochemicals and mining, gas leak detection is directly related to production safety. Electrochemical sensors (such as CO and H2S detection) and PID sensors (VOC detection) are integrated into industrial safety systems to monitor hazardous gas concentrations in real time and trigger alarms immediately if they exceed limits. Semiconductor sensors, due to their cost advantages, are often used for basic monitoring of the environment around factories. The data from these air quality sensors used in industry can also be linked to corporate emission management systems to achieve environmental compliance management.

Smart Buildings and Building Automation

Modern smart buildings deploy multi-parameter air quality sensors (such as composite sensors integrating PM2.5, CO₂, and VOC) to achieve intelligent control of HVAC systems. When CO₂ concentrations exceed 1000 ppm, the fresh air system is automatically activated, or the air purifier's operating mode is adjusted based on PM2.5 data. Temperature and humidity sensors are integrated with air conditioning systems to optimize energy consumption while maintaining air quality. Such applications particularly emphasize the long-term stability and low maintenance requirements of sensors.

Consumer Electronics and Smart Homes

Home air purifiers, fresh air systems, and other devices commonly use low-cost laser PM2.5 sensors and metal oxide VOC sensors. In recent years, portable home air quality sensor with display screen (such as combined products for detecting formaldehyde and PM2.5) have become a new favorite in health-conscious consumption. Smart home systems connect sensor data to mobile apps via IoT technology, enabling remote monitoring and automated scene integration (e.g., automatically activating the purifier when VOC levels exceed thresholds).

Transportation Sector

In-vehicle air quality sensors (AQS) have become standard equipment in mid- to high-end vehicles, typically using vibration-resistant semiconductor or electrochemical sensors to monitor PM2.5, NOx, and other pollutant concentrations inside and outside the vehicle in real time, automatically switching the air conditioning circulation mode. Large sensor networks are deployed in public transportation hubs such as subways and airports, combining passenger flow data to optimize ventilation strategies. Electric vehicle battery compartments are also equipped with special gas sensors to prevent thermal runaway risks.

Healthcare and Health Management

Medical-grade air quality sensors are used in sensitive areas such as hospital operating rooms and ICUs to monitor special parameters such as microorganisms and anesthetic gases in the air. Home healthcare devices (such as asthma monitors) integrate micro gas sensors to help patients avoid allergens. Wearable devices are also beginning to integrate CO and VOC sensors to provide users with personalized health recommendations. These applications require extremely high response speeds and accuracy from sensors.

With the development of IoT and AI technologies, air quality sensors are evolving from single-function detection toward intelligent and networked systems. In the future, more innovative application scenarios will emerge in emerging fields such as smart cities and precision agriculture.