A breathalyzer is a scientific device that is used to measure the concentration of alcohol in an individual’s bloodstream. The term Breathalyzer initially referred to a specific scientific instrument that was developed by an inventor named Robert Frank Borkenstein and that was registered as a trademark in 1958. Today, however, breathalyzer has devolved into a generic term that applies to any number of devices that serve a similar function.

A breathalyzer works by analyzing a person’s breath to detect the level of alcohol that the individual has in his or her body. As an individual drinks alcoholic beverages, the alcohol is absorbed into the bloodstream through the mouth, the throat, the intestines and the stomach. When the blood moves through the lungs, alcohol from the blood is passed into the air sacs and breathed out.

When an individual exhales, the ethanol that is present in his breath is oxidized to acetic acid, which is detectable using a number of different testing methods. When an individual breathes into a breathalyzer test, the ethanol and acetic acid reacts and the level of alcohol is detectable using IR technology, fuel cells or other testing methods. A ratio converts alcohol in the lungs to alcohol in the bloodstream: 2,100 ml of air from the lungs contains the same amount of alcohol as 1 ml of blood.

The level of alcohol in the bloodstream as measured by a breathalyzer or by a blood test is referred to as an individual’s blood alcohol content or BAC. A blood alcohol content or BAC of .08 percent is considered the legal limit and a driver who tests above this limit may be charged with the criminal offense of driving while impaired by alcohol.

While breathalyzers are used to determine if someone should face serious criminal charges, breath tests are not flawless devices. There are different types of breath tests that may be administered by law enforcement officers (LEOs) and all breath tests must meet specific requirements in order to be used as evidence in criminal proceedings.

Individuals accused of drunk driving may raise questions regarding the accuracy of breath tests results and should be represented by an attorney with in-depth knowledge of the breathalyzer test devices that are utilized in the state where the alleged offense occurred.

Types of Breath Tests

Breathalyzer tests can be broadly grouped into different categories including:

  • Passive Breathalyzers: Passive alcohol sensors (PAS) or passive breathalyzers may be attached to a law enforcement officer’s clipboard or flashlight. This type of test has internal fuel sensors that are designed to detect the presence of alcohol when a motorist exhales. A driver does not actively blow into a passive breathalyzer and this test is considered a preliminary test that can provide a police officer with cause to investigate the motorist more closely and perform other sobriety testing. Passive breathalyzers are not generally used as evidence in a court of law.
  • Active Breathalyzers: Active breathalyzers require a driver to blow into a mouthpiece to determine his or her BAC. There are two distinct types of active breathalyzer devices: preliminary breath tests (PBTs) and evidential breath test machines. Both PBTs and evidential breath tests used by law enforcement officers generally utilize different technology than personal active breathalyzer machines that individuals purchase. Breath test machines utilized by individuals generally rely on semiconductor sensors, which less reliable than fuel cell technology or infrared technology used in professional tests.

The tests administered by law enforcement must meet specific criteria to ensure sufficient accuracy and reliability. The Federal Register contains a “Conforming Products List of Screening Devices to Measure Alcohol in Bodily Fluids.” This is a list of all Breathalyzer tests that meet established performance criteria and methods for testing alcohol as set forth by the National Highway Traffic Safety Administration.  Conforming devices on the list found in the Federal Register include but are not limited to:

  • The AlcoScan AL-2500, manufactured by AK Solutions, USA, LLC
  • The AlcoMate Pro and AlcoMate Core, manufactured by AK Solutions, USA, LLC
  • The Alco Check 3000 D.O.T. and the Alco Check 9000, manufactured by Alco Check International
  • The DRIVESAFE, manufactured by Alcohol Countermeasure Systems Corp.
  • The BAC Master, manufactured by BAC Solutions, Inc.
  • The Intoxilyzer 500, manufactured by CMI, Inc.

NHTSA standards apply to both mobile breath tests and to non-mobile breath tests designed for use at a fixed location.

Ignition Interlock Devices, which may be required following conviction for impaired driving, also utilize breathalyzer technology to test a motorist’s BAC before the driver is able to start his vehicle’s engine. Ignition Interlock Devices (IIDs) must pass the National Highway Traffic Safety Administration, Model Specifications for Breath Alcohol Ignition Interlock Devices (BAIIDs).

Preliminary Breath Tests vs. Evidential Test Devices

Preliminary breath tests, or PBTs, are portable devices that are used in the field by LEOs prior to an arrest for intoxicated driving. Motorists are not required to submit to a PBT. However, if a driver refuses to undergo a PBT, he may be required to submit to an evidential breath test or a blood test. Virginia’s implied consent laws indicate that all motorists must have their blood alcohol content tested if law enforcement has reasonable cause to suspect intoxication. A driver who refuses either an evidential breath test or a blood test may face a suspended license and criminal charges and the refusal may be used as evidence in a criminal prosecution for impaired driving.

While PBTs are not as reliable as evidential breathalyzer tests, they are still subject to minimum requirements for accuracy. The Department of Forensic Science  in the state of Virginia has approved multiple PBTs for use by law enforcement officers to determine if a motorist is likely impaired. Approved PBT devices include:

  • Devices manufactured by a Missouri company called Intoximeters, including the Alco-Sensor as well as the Alco-Sensor II, III and IV
  • Devices manufactured by Lyon Laboratories in the United Kingdom, including the CMI SD2 and SD 5
  • Devices manufactured by CMI, Inc. in Kentucky including the Intoxilyzer 400PA
  • Devices manufactured by Lifeloc Inc. including the Lifeloc PBA 3000 and FC10

Preliminary breath test devices are generally solid-state electrochemical devices that have a pass/fail indicator light. Regulators establish requirements for the use of PBTs. In the state of Virginia, the regulations for PBTS are set forth in 6 VAC 20-190-170. The regulations stipulate that PBTs may not have a systematic error rate exceeding 10 percent. According to 6 VAC 20-190-200, the PBT must also be maintained pursuant to instructions set forth by the manufacturer and must be administered according to manufacturer-described protocols.

The 10 percent margin of error is a significant permissible error rate, making this type of breath test notoriously unreliable and inexact. Virginia Code section 18.2-267 thus prohibits the use of PBTs in “any prosecution” for driving while impaired. A pre-trial motion is not considered a prosecution, so a PBT may be used as evidence in Motions to Suppress or certain other pre-trial actions. However, Virginia has created an evidentiary exception for the admission of official blood and breathe test results from evidential tests, but the exception is not applicable to a PBT. Without the evidentiary exception, a prosecutor may be unable to offer a PBT as scientific evidence without an expert witness.

Evidential test devices are distinct from PBTs and are an entirely different type of breathalyzer device. After a motorist is arrested for impaired driving based on the results of a field sobriety test and/or a PBT, officers may take the accused to the police station for an evidential test to be performed. Drivers may also take the accused to a police station for an evidential test if a PBT is refused.

In Virginia, breath tests are the preferred method of evidence collection in impaired driving cases, rather than blood tests. Va. Code section 18.2-268.2  indicates that an evidential blood test is to be performed for motorists accused of impaired driving unless the driver is physically unable to undergo the breathalyzer or unless the breath test is not available. Because breath tests are the preferred method of obtaining evidence of intoxication, blood tests are thus administered as an alternative only in limited cases and breathalyzers are frequently used as evidence in criminal trials for drunk driving.

Evidential test devices perform a quantitative analysis of the level of alcohol in the breath. Evidential devices must be on the National Highway Traffic Safety Administration’s (NHTSA) Conforming Products List (CPL) and must be approved for law enforcement personnel to use in individual states. The state of Virginia first began utilizing instrument-based breath tests to determine BAC in 1972, with the Breathalyzer® the first model to be utilized in the state. The initial Breathalyzer® was dependent upon a chemical reaction that resulted in a color change when alcohol was present.

 In the mid-1990s, the state of Virginia placed the Intoxilyzer 5000® on the list of approved evidential breath test devices in Virginia. This device utilizes infrared (IR) analysis to calculate a result and is the most widely used Breathalyzer test. Virginia’s Intoxilyzer 5000® model was designed specifically for the state and the Division of Forensic Science refers to it as the Intoxilyzer 5000CD/FG5 model. Many other jurisdictions also utilize their own Intoxilyzer models. All modern models of the Intoxilyzer 5000 utilize infrared (IR) testing technology.

 In 2008, Virginia also placed the Intox EC/IR II on the list of approved devices. The Intox EC/IR II utilizes both (IR) analysis and electrochemical (EC) analysis in order to determine an individual’s level of impairment.

Infrared Analysis vs. Fuel Cell Technology

Infrared breath tests such as the Intoxilyzer 5000® are a very common type of breath test technology but are not the only type. Fuel cell technology is also frequently utilized to measure an individual’s blood alcohol content.  The different testing procedures work in different ways. For example:

Infrared Instruments are the most commonly used breath tests because they are stable and reliable and may be automated. The theoretical basis for IR tests are based on the Beer-Lambert Law of Absorption, which demonstrates that molecules absorb electromagnetic radiation at their own specific unique wavelengths. Each molecule has its own infrared fingerprint, including Ethyl Alcohol, which absorbs radiation at wavelengths of approximately 3.0, 3.39, 7.25, 9.18, 9.50 and 11.5. Because no other compound absorbs radiation at all of these wavelengths and only at these wavelengths, a greater absorption of these wavelengths means a higher concentration of alcohol exists. When an IR test is performed, an individual breathes into a sample chamber and an IR energy beam emerges. Energy loss at the appropriate wavelengths is then measured to determine the level of absorption and thus the amount of alcohol that is present. IR tests are generally performed at police stations and are stationary units.

Fuel Cell technology dates back to the 1800s but there was no practical application for fuel cell instruments until researchers at the University of Vienna demonstrated a fuel cell that is specific to alcohol in the 1960s. The alcohol fuel cell consists of a chemically inert layer that is porous and that is coated on both sides by platinum oxide. Fuel cell instruments operate on the principle of electrochemical oxidation and a fuel cell test can determine the level of alcohol concentration in the blood by measuring the electrical reaction that alcohol oxidation causes. A fuel cell test utilizes a device with an acidic electrolyte solution on the porous layer of the alcohol fuel cell. The fuel cell with the electrolyte layer and attached platinum wire electrical components is mounted into a case and the breath sample is introduced into the case through a gas inlet where it then reacts.  Fuel cell technology is common on portable preliminary breath tests used in the field.

Individuals arrested for driving while impaired must determine what type(s) of breathalyzer and/or other blood alcohol content testing was utilized to determine their level of impairment. Understanding which test was utilized is important because there are different requirements for each test type and different ways to challenge the validity of test outcomes for individuals accused of driving while impaired. An experienced attorney with a detailed understanding of breath tests can provide information on options for challenging scientific evidence in your DUI case.