ABSTRACT
Solid-state gas sensors present a high potential for applications where the use of conventional analytical systems such as gas chromatography or optical techniques is prohibitively expensive. The description of miniaturized, handheld, low-cost, solid-state sensors for clinical diagnosis of important pathologies through analysis of the exhaled breath is reported. Resistive gas sensors based on metal oxide semiconductors (MOS) were put in practical use for the first time by Taguchi at the beginning of the 1970s. The main application of these devices was as alarms to prevent accidents in domestic houses by monitoring the presence of hazardous levels of explosive gases. Electrochemical gas sensors are able to detect the majority of common gaseous species and vapor, including CO, H2S, ethanol, acetone, ammonia, SO2 etc. in a wide variety of applications. These sensors are compact, require very little power, exhibit excellent linearity and repeatability, and generally have a long life span, typically 1–3 years.
