Fuel cell breathalyzers are used by individuals desiring the highest level of accuracy, as well as law enforcement officers for roadside screenings, in substance abuse centers, clinics, and in businesses. Fuel cell sensors rely on an electrochemical process that oxidizes the alcohol in a breath sample and produces an electrical current that the breathalyzer measures to determine the BAC. A fuel cell consists of two platinum electrodes that are partitioned by a porous acid-electrolyte material.
As exhaled air passes through the fuel cell, the platinum oxidizes any alcohol present and produces acetic acid, protons and electrons. The electrons flow through a wire from the platinum electrodes and reveal the BAC. The strength of the current corresponds to the volume of alcohol present in the sample.
At higher BAC concentrations, fuel cell sensors offer more accurate readings than traditional semiconductor sensors. They are also not subject to false positives when used by diabetics or those on a low calorie diet. Overall, they are the best, most accurate devices an individual or business can purchase because they deliver a high degree of reliability. Infrared Spectrometry is used in large, table-top breathalyzers often found at police stations and in BACtrack's quality control lab.
Spectrometers work by identifying molecules based on the way they absorb infrared light. The level of ethanol in a sample is singled out and measured, and a subject's alcohol level can then be determined. In addition, law enforcement must wait 15 minutes from when they first encounter a subject before obtaining a breath sample. This is because any residual alcohol in the mouth can affect the reading. For example, if you used mouthwash just before getting pulled over for a potential DUI and taking a breathalyzer test, the readout would be affected because mouthwash has alcohol in it.
The industry standard seems to be a minute wait to declare that any possible mouth alcohol would be gone and absorbed by the body prior to testing. A breathalyzer at a police station is different from the one law enforcement officers have on the road. This machine weighs almost 18 pounds and has a variety of improvements over the PBT. The Intoxilyzer analyzes alcohol using infrared spectroscopy, rather than the somewhat archaic fuel cell method of the PBT.
Without giving a science lesson, infrared spectroscopy is where infrared light passes through a sample of your breath. This breath is also deep lung air, just like with the PBT. Any alcohol molecules in your breath sample will actually absorb some of the radiation of the infrared light. The machine measures the amount of infrared radiation that hits the other side of the chamber against the amount that was started with, and the difference is a measurable amount of alcohol molecules that were present in the sample.
The Intozilyzer is also more advanced than the PBT in that it allows the law enforcement operator to determine if the subject is actually blowing air into the machine. This breathalyzer tells the operator exactly when enough breath has been blown to obtain deep lung air, and the result is printed out on a paper, not just displayed on an LED display.
The Intoxilyzer actually has an audible buzzer that indicates when a proper breath sample is being blown into it. The machine also determines when deep lung air is achieved and takes the sample itself, instead of the officer pressing a button, as with the PBT.
Essentially, the Intoxilyzer takes the human error out of the equation and allows the breathalyzer to do almost everything. In Montana, several cities including Missoula have enacted laws that make it a misdemeanor crime to refuse breath tests. Private criminal defense attorneys in Missoula, MT will typically tell you that if you drank more than 1 alcoholic beverage per hour, you are likely near or over.
Image: Janet Lackey. The standard. Types of Devices There are three major types of breath alcohol testing devices based upon different principles:. Regardless of the type, each device has a mouthpiece or tube through which the suspect can blow air and a sample chamber where the air goes. The rest of the device will vary with the type. Breathalyzer The device contains a system to sample the breath of the suspect, two glass vials containing the chemical reaction mixture and a system of photocells connected to a meter to measure the color change associated with the chemical reaction.
To measure alcohol, a suspect breathes into the device. The breath sample is bubbled in one vial through a mixture of sulfuric acid, potassium dichromate, silver nitrate and water. The principle of the measurement is based upon the following chemical reaction:.
In this reaction, 1. The sulfuric acid removes the alcohol from the air into a liquid solution. During this reaction, the reddish-orange dichromate ion changes color to the green chromium ion when it reacts with the alcohol; the degree of the color change is directly related to the level of alcohol in the expired air.
To determine the amount of alcohol in the expired air, the reacted mixture is compared to a vial of unreacted mixture in the photocell system, which produces an electric current that causes the needle in the meter to move from its resting place. The operator then rotates a knob to bring the needle back to the resting place and reads the level of alcohol from the knob; the more that the operator must turn the knob to return it to rest, the greater the level of alcohol.
Intoxilyzer This device uses infrared IR spectroscopy, which identifies molecules based on the way they absorb IR light. Molecules are constantly vibrating and these vibrations change when they absorb IR light.
The changes in vibration include bending and stretching of various bonds. Each type of bond within a molecule absorbs IR at different wavelengths. The wavelength helps to identify it as ethanol and the amount of IR absorption tells you how much ethanol is there. In the Intoxilyzer, a lamp generates a broadband many wavelengths IR beam. The IR beam passes through the sample chamber and is focused by a lens onto a spinning filter wheel. The filter wheel contains narrow band filters specific for the wavelengths of the bonds in ethanol.
The light passing through each filter is detected by the photocell, where it is converted to an electrical pulse. The electrical pulse is relayed to the microprocessor, which interprets the pulses and calculates the BAC, based on the absorption of infrared light. Fuel Cell Detectors Modern fuel cell technology has been applied to breath alcohol detectors.
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