What's the difference between saliva alcohol testing and a breath alcohol machine?

By John Hawes | Last updated: January 16, 2019

The primary difference between saliva alcohol testing and a breath alcohol machine is the method used to collect the test specimen. A saliva alcohol, or oral fluid alcohol test, requires the subject to submit an oral fluid sample. A breath alcohol machine test is performed using the subject's exhaled breath. Additionally, the two testing methods differ in the type of analysis used to detect the presence of alcohol. Finally, each breath alcohol test collects a single sample that cannot be divided for subsequent testing whereas some saliva alcohol testing permits multiple tests to be conducted using the same specimen. For both a saliva alcohol test and a breath alcohol test, a positive result is confirmed by use of an evidentiary breath alcohol machine.

What types of results do saliva alcohol tests and breath alcohol testing machines provide?

Saliva alcohol and breath alcohol machine tests are both suitable for use as a screening method to detect the presence of alcohol. Both tests can provide an instant positive or negative result. Devices using either saliva or breath testing methods may also provide data indicating subject’s blood alcohol content (BAC) level.

Both saliva and breath tests are designed to detect alcohol that has already been ingested by the test subject and is present in the blood. Once alcohol is consumed and enters the bloodstream, it is present in a person's saliva and also his or her exhaled breath. These two testing methods rely on defined ratios to calculate the equivalent blood alcohol concentration based on the alcohol levels detected in either the saliva or breath respectively.

Saliva Alcohol Test Sample Collection

Oral fluid specimens for saliva alcohol testing may be obtained using an absorbent material placed in the mouth or by collecting a sample of forced expectorant (spit) from the test subject in a collection container. Once collected, the saliva sample is immediately tested using a point-of-collection analyzer. An alcohol saliva test may also be submitted laboratory testing. However, lab-based saliva alcohol testing cannot detect the presence of ethanol alcohol. Instead, a lab-based immunoassay test will detect the alcohol biomarker ethyl glucuronide (ETG). The detection window for this biomarker is variable and does not correlate to a specific blood alcohol concentration. Thus, lab testing of saliva samples is not used to confirm impairment or workplace alcohol violations.

Breath Alcohol Machine Test Sample Collection

The collection of a breath specimen for alcohol breath machine testing may be achieved by active or passive means, depending on the testing device used. Active collection requires the test subject to breathe into a straw or mouthpiece until a sufficient sample has been provided. Passive collection breath alcohol machines use a fan or other mechanical means to capture the test subject's breath vapor when the device is near the subject's mouth.

After collection of a breath alcohol specimen, one of several different methods will be applied to analyze the sample. When an evidentiary breath alcohol machine is used, two different methods may be employed to achieve the most accurate results.

Infrared spectrophotometer and electrochemical fuel cell technology are two of the most commonly employed methodologies for detecting alcohol in a breath sample. Infrared spectrophotometer machines measure changes in light wave patterns caused by the presence of alcohol in the breath. Electromechanical fuel cells machines are most often used in workplace testing. These devices detect the presence of alcohol by measuring electrical activity triggered by the chemical reaction between the alcohol and a catalyst in the device. The results of an alcohol breath machine test are available within minutes.

The U.S. Federal government has designated a limited number of devices as suitable for alcohol screening and confirmation tests when such testing is required by federal law. When testing is required for a safety-sensitive transportation job, an evidentiary blood alcohol machine is always required to confirm a positive screening result.

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Written by John Hawes

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John Hawes is the CCO and co-founder at SureHire Occupational Health Testing. John graduated in 2001 from the University of Alberta with a Bachelor of Science degree in physical therapy. As a former physical therapist, John uses his knowledge of physical therapy and interest in ergonomics and biomechanics to devise fit for work testing.

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