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The assessment of the explosion hazard of a combustible gas mixture is not a trivial task if the type of combustible gases is not known precisely. Typically, the concentration of combustible gas is defined as the response of a catalytic sensor to its presence in the air. It has been known that catalytic sensors have different sensitivities to different combustible gases. Usually gas analyzers are calibrated by methane and are not suitable for measuring other flammable gases without additional correction for each gas. In this paper, we have investigated the dependency of catalytic sensor sensitivity on the sensor temperature for the binary mixture of methane, propane, butane, hexane and hydrogen with air in a wide temperature range. Based on the obtained dependencies, a measurement algorithm and an empirical equation were proposed that allow calculating the concentration of unknown combustible gas in % of LEL. The process of measuring and processing data can be automated using a digital processor. The experimental results have shown that the concentration measurement error is in the range 5%–10% for binary mixture.

Wireless sensor networks (WSNs) have recently been applied for industrial monitoring, including combustible and flammable gases monitoring. In this work, we present a wireless gas sensor node in which a widely used Wheatstone sensing circuit based on two sensors is exchanged with a single sensor circuit, as well as the associate gas measurement procedure. The core of the measurement procedure is the four-stage heating profile, which enables low power consumption of sensing circuit and thermo compensation adjustment. A thermo compensation algorithm is capable of avoiding the effect of the environmental temperature on the measurements by keeping stable zero-offset within $\pm 1\;\hbox{mV}$ and ensuring low absolute error within 0.1% vol. The thorough design of the sensor node allows it to fit into the $5.5\;{\hbox{cm}^3}$ packaging, which ensures its true ubiquitous deployment in outdoor and industrial environment.