Department of Chemistry, University of Bari, via E.Orabona 4, 70126 Bari, Italy.
Sensors (Basel). 2011;11(5):5290-322. doi: 10.3390/s110505290. Epub 2011 May 16.
The complexity of the odours issue arises from the sensory nature of smell. From the evolutionary point of view olfaction is one of the oldest senses, allowing for seeking food, recognizing danger or communication: human olfaction is a protective sense as it allows the detection of potential illnesses or infections by taking into account the odour pleasantness/unpleasantness. Odours are mixtures of light and small molecules that, coming in contact with various human sensory systems, also at very low concentrations in the inhaled air, are able to stimulate an anatomical response: the experienced perception is the odour. Odour assessment is a key point in some industrial production processes (i.e., food, beverages, etc.) and it is acquiring steady importance in unusual technological fields (i.e., indoor air quality); this issue mainly concerns the environmental impact of various industrial activities (i.e., tanneries, refineries, slaughterhouses, distilleries, civil and industrial wastewater treatment plants, landfills and composting plants) as sources of olfactory nuisances, the top air pollution complaint. Although the human olfactory system is still regarded as the most important and effective "analytical instrument" for odour evaluation, the demand for more objective analytical methods, along with the discovery of materials with chemo-electronic properties, has boosted the development of sensor-based machine olfaction potentially imitating the biological system. This review examines the state of the art of both human and instrumental sensing currently used for the detection of odours. The olfactometric techniques employing a panel of trained experts are discussed and the strong and weak points of odour assessment through human detection are highlighted. The main features and the working principles of modern electronic noses (E-Noses) are then described, focusing on their better performances for environmental analysis. Odour emission monitoring carried out through both the techniques is finally reviewed in order to show the complementary responses of human and instrumental sensing.
气味问题的复杂性源于嗅觉的感官性质。从进化的角度来看，嗅觉是最古老的感觉之一，它可以帮助寻找食物、识别危险或进行交流：人类的嗅觉是一种保护性感觉，因为它可以通过考虑气味的宜人/难闻程度来检测潜在的疾病或感染。气味是光和小分子的混合物，与各种人类感官系统接触，即使在吸入空气中的浓度非常低的情况下，也能够刺激解剖学反应：所体验到的感知就是气味。气味评估是一些工业生产过程（如食品、饮料等）的关键点，并且在一些不寻常的技术领域（如室内空气质量）中也越来越重要；这个问题主要涉及到各种工业活动（如制革厂、炼油厂、屠宰场、酿酒厂、民用和工业废水处理厂、垃圾填埋场和堆肥厂）对环境的影响，这些活动是嗅觉滋扰源，也是空气污染投诉的主要原因。尽管人类嗅觉系统仍然被认为是气味评估中最重要和最有效的“分析仪器”，但对更客观的分析方法的需求，以及对具有化学电子特性的材料的发现，推动了基于传感器的机器嗅觉的发展，这种嗅觉有可能模仿生物系统。本文综述了目前用于气味检测的人类和仪器传感的最新技术。讨论了使用经过训练的专家小组进行的嗅测技术，并强调了通过人类检测进行气味评估的优缺点。然后描述了现代电子鼻（E-Nose）的主要特点和工作原理，重点介绍了它们在环境分析方面的更好性能。最后还综述了通过这两种技术进行的气味排放监测，以展示人类和仪器传感的互补反应。
