Smog watch

An inexpensive and portable device could help you monitor the air quality in your neighborhood or be used by environmental researchers checking pollutants leaking into groundwater from waste sites.

David Williams, Head of UCL's Chemistry Department, and his colleagues, post-doctoral researcher Ljiubov Morris and electrochemist Daren Caruana, are working on an instrument for measuring the common pollutants that lead to the all too familiar smog of cityscapes as well as organic solvents and other compounds that can leach into groundwater from underground gas tanks. The researchers expect their device to scoop expensive professional equipment costing hundreds of thousands of dollars by reaching the market at just a few hundred.

David Williams

Volatile organic compounds (VOCs) such as toluene, heptane, xylene, and benzene are readily detectable with the wristwatch device by absorption onto a sensitive pad made from Tenax TA. Controlled heating (temperature-programmed thermal desorption) then releases the pollutants, which are picked up by a built-in solid-state sensor array for analysis. The sensors are based on new commercial technology from Capteur Sensors Ltd, a British company set up ten years ago by Williams and his colleagues and now part of City Technology Ltd.

The researchers emphasise that their mini pollution detector trades off resolution and precise identification of species to achieve sensitivities of the order of 0.1 parts per billion by volume in analysis times of around 40 minutes.

	Daren Caruana

"If this instrument were commercially developed - which should be straightforward - then waste dumps could be comprehensively instrumented to track leaching of solvents into ground water and storage tanks could be monitored for leakage", enthuses Williams. "At present, the UK network of air-quality monitors measures hydrocarbons at just 13 locations countrywide. This new technology is so cheap that you could find out what the air was like outside your house or at the busy junction down the road, rather than globally across the whole city." He adds that the development of inexpensive sensor technology has major implications for how the environment is managed and could have public health benefits, providing a warning of high pollution in a specific area for people with respiratory problems.

Williams believes that the device might also find use in testing for "sick building syndrome", controlling ventilation systems or checking the air in public buildings. He suggests that it should also be possible to track sources of emissions or characterize the hydrocarbon content of the air according to the proportion emitted by diesel or petroleum-powered vehicles.

Measurement Science and Technology, 2002, vol 13(4), 603-612.