By Samudrapom DamReviewed by Susha Cheriyedath, M.Sc.Updated on Nov 19 2024A breathalyzer is a device commonly used to measure the concentration of alcohol in a person's breath, which is an indirect indicator of their blood alcohol content (BAC). Law enforcement agents commonly use the device to test drivers suspected of being under the influence of alcohol.
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Key Components and Functions
A breathalyzer is usually made up of two vials composed of a photocell indicator and a series of chemicals that work together to calculate BAC. A mouthpiece is attached to the breathalyzer, which allows the suspect to blow into the device. During a routine breath test, the breath passes through the vessel to the measurement component of the detector. It collects into a vial containing sulfuric acid, potassium dichromate, silver nitrate, and water.1
Key Principles
When users exhale into a breathalyzer, traces of ethanol react with sulfuric acid and potassium dichromate. These are then oxidized into chromium sulfate and acetic acid. The silver nitrate in the vial catalyzes this chemical reaction.1
A photocell system is then applied to compare the amount of unreacted potassium dichromate left in the vial to the amount of the same chemical used to oxidize ethanol, which will provide a measurement of alcohol content from the breath sample. The photocell system bases its alcohol content measurement on the absorption of light by the potassium dichromate.1
The amount of light absorbed will be proportional to the amount of alcohol in the sample cell. Comparing the reference sample in the breathalyzer and the suspect sample generates an electrical current that moves a needle on an indicator meter.1
One of the main problems with this test is that it consumes the chemicals in the reaction vessel, implying a constant need to calibrate the device and replenish it with the right amount of chemicals to oxidize ethanol so that an accurate reading of alcohol concentration can be produced.1
Based on the principle of molecular exchange through the alveoli in the lungs, by measuring a constant ratio of BAC, an equivalent BAC can be calculated. The average ratio of breath alcohol to the BAC is 2,100:1. By volume, it can be assumed that 2,100 milliliters of the air contained within an alveolar sac in the lungs will contain a similar concentration of alcohol compared to 1 milliliter of blood.1
The modern-day electronic breath testing device is made of two platinum electrode components that surround acid-electrolyte material. Where air passes through the electronic device, the platinum electrodes begin to oxidize the ethanol molecules and via catalysis, this reaction converts the ethanol into acetic acid and a collection of residual protons and electrons.1
The protons and electrons generated as a product of the chemical reaction flow through the electric meter over to the platinum electrode at the opposite end of the meter where they combine oxygen atoms and the residual electrons to form water molecules.1
Based on the proton-electron exchange in a breathalyzer, more alcohol molecules will result in a greater number of electrons generated from a catalytic chemical reaction. The electrons generated then drive the electrical current that is measured by a microprocessor to indicate the amount of alcohol content proportional to BAC.1
Types of Sensors Used
Fuel-cell alcohol sensors: Also called “alcosensors”, fuel-cell alcohol sensors are considered the most prevalent method for testing alcohol content. The alcosensor device is engineered with fuel cells consisting of a porous layer coating, and a platinum sheet covered with an acidic chemical, and works on the principle of electrochemical oxidation.1
The thin sheet of platinum is enclosed in a plastic tube. During a breath test, the suspect exhales air into the plastic tube and transfers the air molecules to the platinum layer. The fuel cells picking up the alcohol, convert the alcohol molecules into acetic acid. Electrons are generated as an end product of alcohol oxidation (2 electrons are generated per molecule of ethyl alcohol).1
Hydrogen ions are also generated and combine with free oxygen atoms in the fuel cell where both elements combine to form water. Excess electrons at the upper surface of the fuel cell generated from the oxidation process can then be compared to the number of electrons at the lower end of the fuel cell.1
As both platinum surfaces are electrically wired, the electrical voltage flowing through a circuit is directly proportional to the alcohol content utilized by a fuel cell. Fuel-cell alcohol sensor technology is ideal for small-scale screening based on the low power resource required to function in this device.1
Infrared sensors: In the United States, intoxilyzers have replaced breathalyzers for measuring alcohol content. Intoxilyzers measure infrared radiation (IR) to a wavelength that reacts with alcohol molecules. The amount of alcohol in a sample is directly proportional to the amount of energy it takes to bend each covalent bond between atoms in each molecule.1
Intoxylizers are far more accurate than a traditional breathalyzer as it will measure the alcohol content in deep lung air. There is a spring valve to a tube that connects to the testing chamber that opens in response to a large exhale of air pressure, to ensure that deep lung air is entering the valve.1
By using this IR breath test, the chances of receiving a false-positive result decrease even if the suspect has little traces of alcohol content only in the mouth (i.e., from the use of mouthwash) because the main sample to be tested can only come from a deep exhale delivering air content from the lungs.1
During a standard intoxilyzer test, the energy from a suspect’s breath travels through a confined sample chamber to an IR filter with a wavelength band that will be able to detect ethanol molecules. As the IR energy travels through the filter, it reaches a detector that converts the energy into an electrical voltage calculated by a microprocessor.1
Semiconductor sensors: Semiconductor breathalyzers measure the alcohol level in a breath sample based on changes in the resistance of the semiconductor material inside the device. In these devices, the semiconductors generate a small standing electrical current.2
The semiconductor surface absorbs alcohol when it comes in contact with the semiconductor, which results in changes in the resistivity. This leads to changes in the electrical current that indicate the alcohol level present in the breath sample.2
The surface effect of these breathalyzers relies on the atmosphere, and thus their sensitivity to alcohol could vary based on the altitude and climate when the test is performed. Semiconductor technology is commonly used in consumer breathalyzer models due to the varying degrees of sensitivity to alcohol in various atmospheres. These breathalyzers can be manufactured inexpensively.2
Breathalyzer Types
Personal breathalyzer: These devices are the simplest of all existing breathalyzers and can be utilized two times a day. Personal breathalyzers are suitable for individuals who are concerned about their safety.3
Professional Breathalyzers: These breathalyzers are used most frequently, almost 200 to 300 times daily, usually by road transport service departments and large enterprises. Additional devices, such as printers that print the analysis results, are often used in the breathalyzer configuration. Professional breathalyzers possess high accuracy, with a margin of error of only 0.01 ppm in their alcohol concentration measurements.3
Special Breathalyzers: These devices are utilized in small industrial enterprises and medical institutions for 10 to 30 times daily.3
Accuracy and Reliability of Breathalyzers
The electrochemical fuel cell breathalyzer is the most reliable among all breathalyzers, while the IR optical sensor breathalyzer/intoxilyzer is the most accurate as it does not wear out with time.3
The calibration interval of the semiconductor breathalyzer is six months, while the interval for IR and electrochemical breathalyzers is 12 months. Based on response rate, breathalyzers with semiconductor sensors possess a relatively low speed, while breathalyzers with an electrochemical sensor possess a high-performance index.3
Semiconductor and photometric breathalyzers strongly depend on the ambient temperature. However, breathalyzers with electrochemical sensors are less dependent on the ambient temperature.3
Sample Contamination: False-Positive Tests
Many products can interfere with alcohol breath tests, such as:
- Mouthwash (which contains 27% alcohol). In this instance, the breath testing device is calculating the alcohol content from the mouthwash as though it is a direct sample from the lungs and thus providing a false 2100: 1 ratio of BAC.1
- Acetone, a naturally occurring chemical produced by the body in response to incomplete digestion, is a potentially interfering substance.1
- Physical activity and hyperventilation have been found to reduce BAC which will interfere with the suspect sample reading.1
Recent Advances and Future Trends
Breathalyzer technology is rapidly evolving, with machine learning at the forefront of innovation. This emerging technology is poised to revolutionize breathalyzers, making them more accurate, efficient, and versatile than ever before.4,5
A work recently published in Sensors proposed a virtual breathalyzer, an innovative approach to detect intoxication from the measurements obtained by the sensors of wrist-worn devices and smartphones. The intoxication detection problem was formalized as the supervised machine learning task of binary classification (sober or drunk). The results from the virtual breathalyzer were validated against an admissible breathalyzer used by the police.4
In another work published in Npj Digital Medicine, researchers focused on machine learning-driven interventions leveraging smart-breathalyzer data to prevent death and disability due to excessive alcohol use. They devised a digital phenotype of long-term smart breathalyzer behavior to predict breath alcohol concentration levels of individuals.5
Key Market Players
Some of the key players in the global breathalyzer market include BACtrack, AlcoDigital, and Drägerwerk AG & Co. KGaA. They supply breathalyzers based on fuel-cell, semiconductor, and IR technologies.
BACtrack has released ultra-compact the BACtrack C8 smartphone personal breathalyzer powered by BACtrack's proprietary BluFire® fuel cell sensor technology that easily and quickly estimates the alcohol level with professional-grade accuracy.6
Similarly, Dräger Alcotest® 7510 from Drägerwerk AG & Co. KGaA is a robust and compact handheld breath alcohol measuring device specifically designed for advanced screening applications and is suitable for use by police as an alcohol screening device.7
Conclusion
In conclusion, breathalyzer technology has advanced significantly, with various types of sensors such as fuel-cell, semiconductor, and IR technologies offering unique benefits in accuracy and reliability. While each type has its strengths and limitations, the integration of machine learning and smart devices promises to enhance the precision and convenience of alcohol detection.
As these technologies evolve, they are expected to become more efficient, accessible, and crucial in promoting safety and public health. Continued innovation in breathalyzer systems will play a pivotal role in addressing alcohol-related issues worldwide.
References and Further Reading
- Electronic Alcohol Breath Analyzers [Online] Available at http://www.craigmedical.com/Breathalyzer_FAQ.htm
- Modern Breathalysers [Online] Available at http://wwwchem.uwimona.edu.jm/courses/CHEM2402/Crime/Breathalysers_Modern.pdf (Accessed on 19 November 2024)
- Comparison Of Breathalyzers Types [Online] Available at https://conf.ztu.edu.ua/wp-content/uploads/2017/05/43-1.pdf (Accessed on 19 November 2024)
- Nassi, B., Shams, J., Rokach, L., & Elovici, Y. (2022). Virtual Breathalyzer: Towards the Detection of Intoxication Using Motion Sensors of Commercial Wearable Devices. Sensors, 22(9), 3580. DOI: 10.3390/s22093580, https://www.mdpi.com/1424-8220/22/9/3580
- Aschbacher, K. et al. (2021). Machine learning prediction of blood alcohol concentration: A digital signature of smart-breathalyzer behavior. Npj Digital Medicine, 4(1), 1-10. DOI: 10.1038/s41746-021-00441-4, https://www.nature.com/articles/s41746-021-00441-4
- BACtrack C8 [Online] Available at https://www.bactrack.com/products/bactrack-c8-breathalyzer (Accessed on 19 November 2024)
- Dräger Alcotest® 7510 [Online] Available at https://www.draeger.com/en_in/Products/Alcotest-7510 (Accessed on 19 November 2024)
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