Laser-Based Gas Analyzer Developed to Detect Air Pollution

Collaborators on an E.U.-funded research project have developed a miniature hyperspectral optics-based air quality monitoring system. Called PASSEPARTOUT, the €6.9 million ($7.4 million) project uses laser technology to detect the smallest amount of toxic gases in large, densely populated regions.

The World Health Organization estimates that 4.2 million people die prematurely from the high levels of toxic gas molecules and particulate matter they breathe in the air outdoors or ambient air pollution. Currently, methods for assessing air quality in urban environments rely on units the size of refrigerators, which can cost up to €100,000 (~$107,000). Low-cost sensors relying on chemical reactions can suffer inaccuracies due to false readings.

PASSEPARTOUT works by using photothermal and photo-acoustic effects from laser pulses or small blasts of laser light. When the laser light hits a toxic gas, the molecule absorbs light energy, giving off a heat signature that is then reported back to the system. The system then identifies what the harmful gas is, as well as how much of it is present. The PASSEPARTOUT system then goes a step further by using quartz tuning fork technology or quartz enhanced photo-acoustic spectroscopy (QEPAS).

“QEPAS is particularly useful for the detection and quantification of trace gases in challenging environments,” said William Whelan-Curtin, coordinator of the PASSEPARTOUT project. “We use a quartz tuning fork with a sharp mechanical resonance to detect the signals generated by the gas sample while suppressing the background noise.”

Whelan-Curtin explains that the tuning fork detects acoustic waves formed by the gas as it oscillates between hot and cold. The wavelengths of the laser can then be made to match the absorption spectrum of the gas, categorically detecting any targeted gas. These include anything from nitrogen oxides to sulfur dioxide, ammonia, methane, carbon monoxide, carbon dioxide, and black carbon.

The project aspires to make its real-time metropolitan networks commonplace in towns and cities. “We would like to make the technology as common as video surveillance by installing a detector on every lamppost,” continued Whelan-Curtin. “As part of the project, we are developing a smartphone app to check air quality in real-time. In the future, we hope this can be integrated into Google Maps so that your journey to and from work or school can show you not just traffic hotspots but also the route with the cleanest air.”

The PASSEPARTOUT team is currently trialing their technology in landfill sites, seaports, at the University of Bari in Italy, and in a selection of schools in Cork, Ireland. The project is coordinated by Munster Technological University and includes 19 other partners from academia and industry. It will conclude in 2024.