Natural phenomena like volcanic eruptions, wildfires, and sandstorms, along with human activities, release gases and particles into the atmosphere that contribute to ambient air pollution. The fine particles that pollute the air mostly come from human activities such as burning fossil fuels for electricity generation, transportation, waste combustion, agriculture, and the chemical and mining industries.
A Public Health Issue
Exposure to this pollution has negative effects on both the environment and health. In 2019, 99% of the world's population lived in areas where air pollution levels exceeded the limits set by the World Health Organization (WHO) guidelines, increasing the risk of illnesses such as heart disease, stroke, chronic obstructive pulmonary disease, cancer, and pneumonia.
Accordingly, the WHO recommends reducing PM10 particulate matter pollution from 70 to 20 micrograms per cubic metre and PM2.5 from 35 to 10 micrograms per cubic metre. Particles are classified based on their size. While PM10 particles (with a diameter of less than 10 micrometres) are trapped in the nose and upper airways, PM2.5 particles can penetrate deep into the body and reach the brain, potentially impairing cognitive abilities.
How to Measure Air Quality?
In Canada, it is very challenging to accurately measure the real impact of air quality on the population. We have few devices in cities to collect data, primarily because truly effective devices are very expensive. In addition to the acquisition cost, there are installation, operation, and maintenance expenses. Sensors need to be recalibrated three to four times a year. Consequently, accurately representing air quality measurements at a local level is not feasible without spending significant amounts of money to increase the spatial density of measurements. Therefore, it is difficult to inform a specific population about the air quality in their neighbourhood. This is only possible for significant changes in air quality over large spatial scales.
If cities choose to use less expensive sensors to increase measurement density, their data will be less reliable in the medium and long term and less accurate in the short term. Consequently, the results obtained will not reflect reality in cases of small changes in air quality. Once again, it will be challenging to establish links between minor local changes in air quality and the health of a given neighbourhood's population.
Types of Sensors
There is a wide variety of sensors, including contact sensors and proximity sensors. Some are fixed, while others are mobile, depending on the application’s needs.
In the context of an environmental management plan, most of the sensors used are certified for regulatory compliance and are priced at $65-70K. Other types of sensors, although not certified, are recognized by the government for measurement purposes and are priced at around $15K. They are reliable over a good range of concentrations.
There is also a range of low-cost sensors on the market, priced at less than $500 per unit. These sensors are sensitive to factors such as temperature and humidity variations in the air, and their performance is limited, especially at low particle concentrations. However, their low cost allows for multiple deployments, providing a form of representativity of the emission phenomenon.
All these sensors use different technologies.
Main Technologies
Filter Sensors
Filter sensors capture particles in the air on a filter and measure their mass to assess pollutant concentration. This method is precise and reliable, making it suitable for regulatory air quality monitoring, but it requires laboratory analysis and regular maintenance.
Optical Sensors
Optical sensors use light beams to detect airborne particles. When a particle passes through the light beam, it scatters the light, and this scattering is measured to estimate the concentration and size of the particles. These sensors provide real-time monitoring and are highly sensitive.
Lidars
Lidars (Light Detection and Ranging) emit laser pulses and analyze the backscattered light to detect airborne particles over large distances. This technology enables the three-dimensional mapping of pollutant distribution and is ideal for environmental and industrial monitoring.
INO has developed a specialized lidar to meet the unique needs of industrial environments. It stands out due to its high spatial resolution (1 m³ at 150 m) and temporal resolution (one concentration map, or more, per minute), which is essential for identifying dust sources and taking targeted corrective actions.
