What is a Breath Alcohol Test?

A breath alcohol test measures the concentration of alcohol in the blood by analyzing the level of alcohol in exhaled air. Breath alcohol testing may be performed on a person who was involved in a motor vehicle accident to determine if he or she was legally intoxicated at the time of the accident.

Types of alcohol tests

The new techniques and the growing request of the market have lead to an increased development of models of alcohol breath tests. The complexity and big variety of the tests have created confusion among the large consumers but also professionals. We present now a classification of those tests on the following criteria's: the final applications, the breath sampling method, mobility and portability of the tests and the alcohol measurement technology.

Purposes of breath alcohol tests

Screening devices test the subjects to see if their blood alcohol is above the relevant legislation levels or not; it is used in traffic law enforcement, industrial safety programs and in various branches of medicine;
Evidential tests are made to collect the evidence of alcohol concentration and to be further used in a court or industrial tribunal;
Interlock testers are designed for permanent connection to the electrical system of a vehicle; the purpose is to prevent or deter its operation by persons with more than a permitted level of alcohol in their system;
Self-testers are used by people to check their own BAC before driving or working; they have a high degree of accuracy and reproducibility, but are not admissible in court.

Breath sampling method

Active test - the subject blows through a mouth piece into the tester to provide a sample of alveolar breath; he has to cooperate for this;
Active test without a mouth piece - the person blows into an instrument without touching it; there is no mouth contact and mouthpiece is not required;
Passive test - the subject doesn't blow but it is the device that sucks the air from in front the subject's face; they have a smaller degree of accuracy and can give false results.
Portable tests are small, without an external power source; they can be easily carried and used; most of them are hand-held devices and some have also small printers;
Mobile tests, unlike portable testers, require a continual external source of power and they are usually connected to a vehicle;
Stationary tests are non-portable and non-mobile and can be use only in a fixed location such as police stations.

Alcohol measurement technology

A fuel cell sensor is an electrochemical device in which the alcohol undergoes a chemical oxidation reaction at a catalytic electrode surface to generate a quantitative electrical response; they are highly analytical and reliable under various field conditions but expansive and need periodic calibration;
Semiconductors are small beads of a transition metal which come in contact with alcohol; alcohol is then absorbed on the surface, changes the resistance and hence the standing current; this change in current is taken as a measure of the alcohol concentration;
Infrared absorption - organic substances absorb infrared light at various wavelengths depending on their atomic and molecule structure; they can measure the shape of the alcohol concentration curve during the course of an expiration which allows the presence of both deep lung breath and mouth alcohol to be detected;
Gas chromatography involves injecting a small quantity of breath into a heated separated column, through which it is then forced by a carrier gas; the volatile components of the gas are separated from each other as they pass through a column and enter a detector in discrete bands;
Calorimetry involves the oxidation of alcohol by potassium dichromate, resulting in a yellow to green color change. The analytical principle is also used in disposable alcohol detector tubes (the bag and tube) for screening purposes;
Dual sensing are instruments, which combine infrared and fuel cell.

Resources

Breathalyzers.net - distributes several different hand-held alcohol testers, including the highly regarded AlcoMate Digital hand-held unit for consumers, and the Lifeloc FC for professional use.

KeRo Corporation - manufactures and distributes the coin-operated, Alcohol Alert! talking alcohol breath tester.

Also see:

Alcohol breath tester
Types of alcohol tests
Alcohol testing using saliva
Breath alcohol analysis
Blood alcohol testing