From the NILU Annual Report 2019: Road dust and wood burning are well-known sources of particulate matter in Norwegian cities, but industry and construction sites are also where workers may at times be exposed to high levels of particulate matter in their daily lives. In a new project, NILU has developed services that can provide more detailed information on real-time pollution levels in industrial workplaces.
It can be harmful to inhale too much particulate matter (PM) – but how do you know when you have reached the limit? To answer that question, Kjeller Innovation initiated the project “Leopard”, to which NILU – Norwegian Institute of Air Research contributed significantly. The aim of the project was to develop a small, portable sensor that measures particulate matter of different sizes in real time with high accuracy, and warns of high concentrations of particulate matter in the air.
The creation of a dust sensor
“It has been a very exciting project, which resulted in new products and services that NILU can offer in the future”, says senior scientist Matthias Vogt.
“As a first step, we used what’s called CAD drawing (computer-assisted design). The drawing was the starting point for a small, lightweight sensor that could measure particulate matter of different sizes and with high accuracy”, he elaborates. “At the same time, it had to be able to calibrate itself, automatically and in real time, to adapt to the concentrations of particulate matter in the surrounding air.”
To get the best result, NILU hired senior scientist Tuan-Vu Cao, who holds a doctorate in electrical engineering. As key designer and technical coordinator, he worked with developing the sensor in the Leopard project. His knowledge of light scattering, mechanics, air currents and calibration of sensors was crucial in being able to create the suspended dust sensor for the project – but also as part of NILU’s products and services in the future.
A complementary approach…
As a complementary approach to the design of the sensor, scientist Islen Vallejo and engineer Torbjørn Heltne from NILU used an iterative methodology between mechanical design and computer experiments to better understand what goes on inside the sensor – before it was put into production.
Computational fluid dynamics (CFD) enables simulation of how the geometry affects the flow of air with different levels of pollution as it moves through the sensor. At the same time, it is possible to observe how the components of the pollution behave on the inside of the sensor. For example, do particles of different sizes move through the sensor at the same speed, or will some particles settle on the sensor wall? CFD can be used for both gas and particle sensors.
…that opens up new opportunities
“This way, we can find out exactly how the sensor will behave in real situations and under different meteorological conditions”, Vallejo explains. “It can save us many months of field testing.”
The same principle can also be used to test low-cost air quality sensors, which are usually unable to provide measurement data of adequate quality.
“We can use and adapt these algorithms to improve the data quality from the low-cost monitoring instruments”, Vallejo continues. “It will also make it possible to install large networks of affordable air quality sensors across an entire city, to measure air quality in real time at various locations in the city. This is an important service, which NILU can now deliver to municipalities and other stakeholders.”
Testing under real conditions
A major metal manufacturer was very interested in the Leopard project and made its production halls available to test the sensor under real-life conditions.
“It turned out that both employer and employees had limited knowledge about particulate matter pollution”, says Vogt. “Obviously they conducted indoor air quality surveys in line with the Working Environment Act, and as long as the pollution level was within the legal limit, they assumed everything was fine. But that’s not necessarily the case, because even PM levels that are within the limit can lead to health damage if ultra-fine particles are inhaled deep into the lungs”, he explains.
As the manufacturing firm involved gained access to more information about the composition of particulate matter and how the various particles can damage people’s health despite low levels, they became very interested. Previously, they had been unaware that the levels of pollution that could vary in different parts of the factory, as the levels are linked to the various emission sources, work processes and structure of the building at each individual site. For the employers, this prompted a desire for even more information from the Leopard project.
“With our method, we were able to map real-time pollution levels in the entire work area”, says Vogt. “Thus, we could identify different sources of pollution. The dialogue with scientists made the employer more aware of the issue, and our information gave the employer a greater sense of ownership.”
“Based on the results of the project, the metal manufacturer has now initiated construction measures to reduce the level of suspended PM in one of the halls we investigated, to protect workers from PM-related health damage. This is great”, says a satisfied Vogt.
Thus the Leopard project has opened up for new services that NILU can offer to industry and other customers.