Breath analysis has attracted human beings for centuries. It was one of the simplest methods to detect various diseases by using human smell sense only. Advances in technology enable to use more reliable and standardized methods, based on different gas sensing systems. Breath analysis requires the detection of volatile organic compounds (VOCs) of the concentrations below individual ppm (parts per million). Therefore, advanced detection methods have been proposed. Some of these methods use expensive and bulky equipment (e.g. optical sensors, mass spectrometry –MS), and require time-consuming analysis. Less accurate, but much cheaper, are resistive gas sensors. These sensors use porous materials and adsorptiondesorption processes, determining their physical parameters.We consider the problems of applying resistive gas sensors to breath analysis. Recent advances were underlined, showing that these economical gas sensors can be efficiently employed to analyse breath samples. General problems of applying resistive gas sensors are considered and illustrated with examples, predominantly related to commercial sensors and their long-term performance. A setup for collection of breath samples is considered and presented to point out the crucial parts and problematic issues.

This paper presents a portable exhaled breath analyser, developed to detect selected diseases. The set-up

employs resistive gas sensors: commercial MEMS sensors and prototype gas sensors made of WO3 gas

sensing layers doped with various metal ingredients. The set-up can modulate the gas sensors by applying

UV light to induce physical changes of the gas sensing layers. The sensors are placed in a tiny gas

chamber of a volume of about 22 ml. Breath samples can be either injected or blown into the gas chamber

when an additional pump is used to select the last breath phase. DC resistance and resistance fluctuations

of selected sensors using separate channels are recorded by an external data acquisition board. Low-noise

amplifiers with a selected gain were used together with a necessary bias circuit. The set-up monitors other

atmospheric parameters interacting with the responses of resistive gas sensors (humidity, temperature, atmospheric

pressure). The recorded data may be further analysed to determine optimal detection methods.