The EU-funded MACAO project introduced efficient and accurate micro-analysers for detecting and analysing the circulation of various gaseous pollutants generated in aircraft cabins or stemming from air conditioning systems. The new tools can monitor the harmful volatile organic compound (VOCs) and ozone concentrations at unprecedented speed, including species that have never been detected before.
Aircraft cabin: A chemistry laboratory of sorts
An aircraft cabin can be many things, such as a lounge, snack bar, movie theatre or duty-free shop, but it can also be a space of a cumulative cocktail of pollutant gases. The air wafting inside an aeroplane is a combination of recycled air within the cabin along with outside air that is compressed by the aircraft’s engines. VOCs and ozone can also find their way into the cabin, but especially ozone, when the aircraft is flying high near the ozone layer. Unwanted by-products of engine combustion, such as nitrogen oxides, can also pollute the cabin, while other pollutants emanate from within the cabin – ethanol in alcoholic beverages can evaporate and interior furnishings can release formaldehyde. All these pollutant gases present concerns for the health and comfort of passengers and crew. Prolonged exposure to elevated ozone and VOC levels are linked to headaches and respiratory and cardiovascular issues.
Fast, high-sensitivity analysis
MACAO aimed to provide a route around these issues. The project developed two analytical instruments based on microfluidic devices for measuring the concentrations of major air pollutants in aeroplanes. One micro-analyser measures concentrations of various VOCs whereas the other measures ozone concentrations. Technical progress on the VOC microanalyser was excellent. A benzene analyser equipped with a new pre-concentration unit was successfully developed and validated under laboratory conditions, demonstrating the capability of the prototype to adsorb and to desorb the targeted organic species. “The patented instrument successfully detected VOC concentrations of 60 parts per million with a sample of only 20 ml of air,” notes Stéphane Le Calvé, project coordinator of MACAO and research director at the French National Centre for Scientific Research (CNRS). With a detection limit of 3.6 picogrammes, the new device is about 40 to 260 times more sensitive compared to state-of-the-art portable miniaturised instruments (with detection limits of 140 to 940 picogrammes). One of the advantages of the newly developed technologies is that sampling and analysis times are very fast. “Requiring a small air sample collection, the devices shorten the sampling time to around 4 minutes before analysis, which lasts for 10 minutes. In fact, it is possible to conduct air quality analysis every 15 minutes,” explains Le Calvé. What is particularly innovative in MACAO is that up to now there haven’t been any suitable instruments specifically designed to measure the VOCs and ozone concentrations that circulate in the cabin environment. Being able to analyse very small quantities of these gases using microfluidic devices is relatively new. The MACAO team now seeks to further advance the microanalysers and integrate more powerful software to make them fully automatic and more robust. All these factors are essential for a demonstration in real flight conditions.
MACAO, volatile organic compounds (VOC), ozone, pollutant, aircraft cabin, air quality, microfluidic devices