Page 19 - November December Issue
P. 19
How Do Breath Machines Work?
Electrochemical (Fuel Cell) Detection
The fuel cell was developed by NASA for use in its space missions in the 1960s. The fuel cell would produce
electricity from the oxidation of hydrogen in the presence of oxygen. The electrochemical detectors used
in breath testing instruments are based on the same principle. The alcohol in a subject’s deep lung or end-
expiratory breath is oxidized using oxygen and electrodes to generate an electrical current (see Figure 2). The
electrical current generated is proportional to the amount of alcohol in the breath sample. EC detectors are very
reliable, fast, and accurate, but do not have a mouth detection system found in IR detectors.
Figure 2: The Electrochemical or Fuel Cell Detector
Infrared (IR)detection
IR detectors are the most commonly used sensor in evidential breath alcohol instruments. Certain wavelengths
of infrared light (i.e. light which has a longer wavelength than visible light) will be absorbed by alcohol. Typi-
cally the maximum absorption occurs at IR wavelengths around 3.4 and 9.4 microns, which is why all breath
testing instruments use some combination of IR in this wavelength range.
The IR detection system of the Intoxilyzer 5000 is illustrated below (Figure 3).
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Electrochemical (Fuel Cell) Detection
The fuel cell was developed by NASA for use in its space missions in the 1960s. The fuel cell would produce
electricity from the oxidation of hydrogen in the presence of oxygen. The electrochemical detectors used
in breath testing instruments are based on the same principle. The alcohol in a subject’s deep lung or end-
expiratory breath is oxidized using oxygen and electrodes to generate an electrical current (see Figure 2). The
electrical current generated is proportional to the amount of alcohol in the breath sample. EC detectors are very
reliable, fast, and accurate, but do not have a mouth detection system found in IR detectors.
Figure 2: The Electrochemical or Fuel Cell Detector
Infrared (IR)detection
IR detectors are the most commonly used sensor in evidential breath alcohol instruments. Certain wavelengths
of infrared light (i.e. light which has a longer wavelength than visible light) will be absorbed by alcohol. Typi-
cally the maximum absorption occurs at IR wavelengths around 3.4 and 9.4 microns, which is why all breath
testing instruments use some combination of IR in this wavelength range.
The IR detection system of the Intoxilyzer 5000 is illustrated below (Figure 3).
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