Gasification is the process of producing combustible gases from solid materials such as coal,
biomass or solid waste. The laboratory of Space Physics and Energy has two experimental gasifiers
producing synthetic gases whose natures and concentrations must be determined. To do this,
lower-cost sensors were purchased and used for determining the concentration of carbon monoxide
with maximum concentration of 1.000 and 2.000 ppm. Hydrogen and methane concentration was
not offered by these two commercial gas analyzers. In this paper Metal-Oxide gas sensors were
used to extend the measurement range of carbon monoxide up to 4.000ppm. Hydrogen and
methane concentrations up to 10.000ppm in synthetic gas produced by a wood fired co-current
downdraft gasifier measurements were also enabled. These sensors have a chemical sensing
element based on a layer of tin dioxide (SnO2); whose resistivity is sensitive to nature of the gas
between two sensing electrodes. This property gives these sensors a resistive electrical model
whose measurand is the concentration of the input gas. This study shows that resistor R of the
sensor is related to the gas concentration with an equation of the form: log(R/R0) = A log (x) +B.
With A= -0.3072, B = 0.921 for methane, A= -0.6527, B=1.3055 for carbon dioxide and A= -1.522, B
= 4.5686 for hydrogen.

Gasification; modelling; concentration; carbon monoxide; hydrogen; methane.