A Portable Gas Analyzer

This paper describes a portable gas analyzer designed to measure oxygen and carbon dioxide concentrations in samples too small to be assayed by commercial analyzers. The commercial analyzers require a sample of 50 to 100 milliliters, whereas this analyzer requires a sample of less than 4 milliliters. The capacity to analyze small samples makes this apparatus extremely useful for measuring oxygen and carbon dioxide in the microenvironment of wood-decaying fungi. The instrument consists of three components: a 20-milliliter syringe that serves as a mercury reservoir and as a means of passing the sample into the absorption chambers; a manometer that serves as a sampling tube; and two absorption chambers for removing oxygen and carbon dioxide from the sample. The instrument was compared to commercial instruments for accuracy, and a linear regression analysis was made on the results. The equation from 0to 30 percent is Y = 0.029 1.055X, with X and Y expressed as, percents, and has an r2 of 0.998. If samples of 3.5 milliliters are used, the concentration can be measured to the nearest 0.2 percent. This is the same precision obtained with commercial analyzers using a volume of 100 milliliters. The instrument weighs slightly over 20 pounds, costs approximately $50, and is rugged enough for field use. The time required to analyze a sample is less than half that required for the commercial analyzers, and the absorbing liquids last several times longer because of the small sample size.

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