Air Quality Measurement: Understanding The Factors And Techniques

Air quality is a critical factor in maintaining a healthy living environment. Clean air improves public health by reducing health issues associated with air pollution, such as severe asthma, decreased lung function, and premature death. It also has positive economic effects, as improved health leads to reduced medical costs and absenteeism rates. Poor air quality, on the other hand, can increase the risk of respiratory issues, cardiovascular disease, and cancer. Therefore, monitoring and improving air quality is essential for the well-being of people and the planet.

So, how can we measure air quality? The most common method is through the Air Quality Index (AQI), which works similarly to a thermometer, with scores ranging from 0 to 500. The AQI provides a numerical representation of the level of air pollution in a given region, with higher scores indicating worse air quality. This index is divided into six categories, each associated with a specific colour, to indicate the level of concern. Other methods for measuring air pollution include air pollution calculators, air emissions monitoring, and air quality forecasting via interactive maps. These tools help public health officials make informed decisions and develop strategies to improve air quality and protect public health.

Air Quality Index (AQI)

Air quality is measured using the Air Quality Index (AQI). The AQI is a scale that runs from 0 to 500, similar to a thermometer, but instead of showing temperature changes, it indicates the amount of pollution in the air. The higher the AQI value, the greater the level of air pollution and the greater the health concern.

The AQI is divided into six colour-coded categories, each corresponding to a different level of health concern. An AQI value of 50 or below is generally considered safe, with little to no risk to public health. When the AQI value exceeds 50, the air quality is deemed unhealthy for certain sensitive groups of people, such as those with heart and lung diseases. As the AQI value increases further, the health risks become more widespread, affecting larger portions of the general public.

The six categories of the AQI are:

• Green: Air quality is satisfactory, and air pollution poses little or no risk.
• Yellow: Air quality is acceptable, but there may be risks for sensitive individuals.
• Orange: Unhealthy for sensitive groups, including children, the elderly, and people with heart and lung diseases.
• Red: Some members of the general public may experience health effects, while sensitive groups may experience more serious health issues.
• Purple: Health alert—the risk of health effects is increased for everyone.
• Maroon: Health warning of emergency conditions—everyone is likely to be affected.

The AQI is an essential tool for communicating about outdoor air quality and associated health risks to the public. It helps people understand the potential dangers of air pollution and take necessary precautions to protect their health. By monitoring and understanding the AQI, individuals can make informed decisions about their activities and exposure to outdoor air, especially in areas with high levels of air pollution.

Air pollution calculators

One notable example is the calculator developed by the United Nations Environment Programme (UNEP) in collaboration with IQAir. This calculator, released in 2021, offers a real-time estimate of air pollution exposure by processing data from over 6,000 locations worldwide. It prioritises PM2.5 readings, which refer to particulate matter with a diameter of 2.5 micrometres or less, as these particles pose the greatest health risks when inhaled. By applying artificial intelligence, the calculator estimates population exposure to air pollution on an hourly basis.

Additionally, calculators may incorporate data from different sources, including governmental, crowd-sourced, and satellite-derived air quality monitors. By aggregating this data, calculators provide an Air Quality Index (AQI) reading, which is a scale from 0 to 500 that indicates the level of pollution in the air. An AQI value of 50 or below is generally considered safe, while readings above 100 are deemed unhealthy.

These calculators are particularly useful for governments and organisations aiming to improve air quality and protect public health. They enable the identification of air pollution hotspots and facilitate targeted actions to mitigate the impact of pollution on the environment and human well-being.

Air emissions monitoring

Ambient Air Quality Monitoring

Ambient air quality monitoring involves collecting and measuring samples of ambient air pollutants. This process evaluates the cleanliness of the atmosphere by comparing it to established clean air standards and historical data. The aim is to understand the overall air quality in a specific geographical region or area. Government agencies, such as the US Environmental Protection Agency (EPA), use this data to determine compliance with National Ambient Air Quality Standards (NAAQS) for criteria pollutants. These criteria pollutants include carbon monoxide (CO), nitrogen dioxide (NO2), particulate matter (PM2.5 and PM10), and more.

Stationary Source Emissions Monitoring

Stationary source emissions monitoring focuses on individual stationary sources of emissions, such as facilities, manufacturing plants, and processes. This type of monitoring collects and utilizes measurement data to assess the performance of emission control devices and verify compliance with regulatory requirements. For example, a Nitrogen Oxides (NOx) Continuous Emission Monitoring System (CEMS) is used to monitor the NOx concentration in the effluent from a process stack of a stationary source, ensuring compliance with NOx emissions limits.

Air Quality Index (AQI)

The data collected from air emissions monitoring is crucial for calculating the Air Quality Index (AQI). The AQI is a scale that runs from 0 to 500, similar to a thermometer, indicating the level of air pollution. An AQI value of 50 or below is generally considered safe, while readings above 100 are deemed unhealthy. The AQI is categorized into six colour-coded levels, ranging from Code Green (safe for everyone) to Code Maroon (indicating emergency conditions due to extremely unhealthy air).

Air Quality Monitoring Instruments

Air quality monitors are equipped with sensors designed to detect specific pollutants. Some instruments use lasers to scan and measure particulate matter density in a given volume of air. Satellite imaging is another important tool, providing valuable data by measuring the energy reflected or emitted by the Earth. Satellites like those in the NOAA’s GOES-R Series and the Joint Polar Satellite System (JPSS) monitor particle pollution and provide measurements of aerosol concentrations and movement.

Global Air Quality Concerns

According to the World Health Organization, a staggering 99% of the global population breathes unclean air, leading to approximately seven million premature deaths annually. Fine particulate matter, such as PM2.5, poses the greatest health risk as it can be inhaled deep into the bloodstream and is linked to serious illnesses, including stroke, heart disease, lung disease, and cancer. Therefore, strengthening air quality regulations and monitoring capacity is crucial to address this global air pollution crisis.

In conclusion, air emissions monitoring is a comprehensive and ongoing process that utilizes various techniques and instruments to assess the quality of the air we breathe. By measuring specific air pollutants and tracking their sources, governments, organizations, and scientists can make informed decisions to protect public health, mitigate environmental degradation, and develop effective policies to improve air quality on a global scale.

Air quality forecasting via interactive maps

Air quality is a measure of how clean or polluted the air is. Monitoring air quality is important because polluted air can be detrimental to human health and the environment. According to the World Health Organization, 99% of the global population breathes unclean air, and air pollution causes 7 million premature deaths annually.

Air quality is measured with the Air Quality Index (AQI), which works like a thermometer that runs from 0 to 500. The AQI tracks changes in the amount of pollution in the air, with higher values indicating a greater density of pollutants in the air. An AQI of 50 or below is generally considered safe, while readings above 100 are deemed unhealthy.

Interactive maps are a valuable tool for air quality forecasting, providing a visual representation of air quality data across different locations. These maps typically incorporate data from various sources, including ground-based instruments, satellites, and crowd-sourced information. For example, the AirNow Interactive Map includes data from air quality monitors in the U.S., Canada, and Mexico, providing real-time information on the air quality in these regions.

The maps are often colour-coded to indicate the level of air quality, with specific colours corresponding to different categories of health concern. For instance, Code Green and Yellow indicate that the air is generally safe for everyone, while Code Orange signifies that it is unhealthy for sensitive groups, and Code Red and Purple indicate that the air quality is unhealthy for all individuals.

By using interactive maps, users can access detailed information about the air quality in their specific area or region. These maps can help individuals make informed decisions about their activities, especially those who are sensitive to air pollution, such as children, the elderly, or people with heart and lung diseases. Additionally, interactive maps can assist researchers and policymakers in identifying air pollution hotspots and implementing targeted measures to improve air quality and protect public health.

Overall, interactive maps play a crucial role in air quality forecasting, enabling users to visualize and understand the air quality in their surroundings, make informed decisions, and take necessary precautions to safeguard their health and well-being.

Air quality monitors

There are a variety of air quality monitors on the market, from low-cost options to more expensive, comprehensive monitors. The cost of a monitor is not necessarily indicative of its performance—more expensive monitors may simply have additional features such as display quality, housing, the number and type of sensors used, power source, internet connectivity, and how the information received from the sensor is processed.

When choosing an air quality monitor, it is important to consider what types of sensors you need. Nearly every air quality monitor will have a PM2.5 sensor, but other sensors will depend on the monitor in question. For example, if you are looking for a complete indoor air pollution monitor, you may want a VOC sensor as VOCs tend to pose a more significant threat indoors than outdoors.

It is also important to check for official accuracy testing of the monitor and its sensors. While not every monitor has such testing or will advertise it, some air quality monitors have undergone testing by independent organisations.

Best Indoor Air Quality Monitors:

• Airthings View Plus: This monitor is simple and user-friendly, but expensive and lacking in advanced functionality. It has a wide range of sensors, a minimalistic design, and an intuitive app and web dashboard.
• AirGradient ONE: This monitor is open-source and can be purchased as a DIY kit or fully assembled. It has high-quality components from trusted manufacturers and a small OLED screen. It is more suitable for technical users.
• Qingping Air Quality Monitor (Gen 2): This monitor has a beautiful, high-resolution touchscreen and a great user experience. It is affordable and has a good range of sensors, although the battery life is minimal.
• Qingping Air Quality Monitor Lite: This is a very small, compact, and unobtrusive device. It has great connectivity options and a temporary portable battery, although the screen is small and only displays one measurement at a time.
• IKEA Vindstyrka: This is the lowest-cost indoor air quality monitor that can be comfortably recommended. It offers fantastic performance for the price, although it requires an IKEA DIRIGERA Hub for connectivity and only shows qualitative VOC values.

Best Portable Air Quality Monitors:

• AirBeam 3: This monitor is uniquely portable and has a range of features. It has an internal SD card, optional SIM connectivity, and a built-in GPS. It takes readings every few seconds, making it well-suited for outdoor use, although the temperature and humidity sensors are unreliable.
• Atmotube PRO: This monitor has excellent battery life and a great variety of sensors. It has good connectivity and an included carabiner for portability, although the app can be slow.

Best Outdoor Air Quality Monitors:

• PurpleAir Zen: This is one of the most famous air quality monitoring brands. It has dual particle sensors for better accuracy and supports both indoor and outdoor monitoring. It also supports micro SD cards for offline data storage.
• AirGradient Open Air: This monitor is inexpensive, accurate, and fully open-source with user-replaceable parts. It supports community-driven air quality maps such as OpenAQ.
• CO2.Click Model X: This monitor is made by a small Canadian company and has a low cost compared to other outdoor monitors. It has a simple design and a straightforward web portal, although it only has a single PM sensor.

Frequently asked questions