Section 69 Dry Gas Accuracy Tests and Calibration

• Library: DWI Experts and the Science of Chemical Tests 2014

The dry gas is (usually) an NIST (National Institute of Standards and Testing)-traceable cylinder under pressure, which when opened will deliver ethanol gas at a predetermined concentration.

Compressed ethanol gas has also been shown to be a reliable method of calibration and determination of accuracy on breath testing devices. L.D. Silverman et al., Confirmation of Ethanol Compressed Gas Standard Concentrations by an NIST-Traceable, Absolute Chemical Method and Comparison With Wet Breath Alcohol Simulators, 21 J. ANALYTICAL TOXICOLOGY 369–72 (Sept. 1997).

Unlike human breath, a compressed gas, also called a dry gas, does not contain any water, whereas a simulator sample has a water component making it more representative of a human breath sample. If water affects the analysis of a sample, an adjustment of some sort needs to be made to ensure that water components of a breath sample...