How Does The Breath Test Work?

There is a really scientific way of explaining how the breath test works and a really easy way.

Scientific: The Intoxilyzer 9000 uses the concept that alcohol molecules absorb light energy at specific wavelengths to measure ethyl alcohol concentration in breath samples. The wavelengths of infrared light used are in the 8 and 9 micron regions. The heart of the Intoxilyzer 9000 instrument is a self-contained heated optical bench. This optical bench consists of the heated sample chamber, pulsed infrared light source and the pyroelectric detector. The sample chamber within the Intoxilyzer 9000 consist of two preheat chambers and the final sample chamber. At one end of the chamber the light source, a Micro-Electro-Mechanical System based infrared source, emits infrared light energy. This energy is directed through the chamber by a lens. At the other end of the chamber is a pyroelectric detector which changes the heat energy of the light source into an electrical response. This electrical response is then used to calculate the breath alcohol concentration (BAC) of the sample.

The determination of the BAC is based on the amount of light energy striking the detector. When no alcohol is present the infrared light passes through the chamber unaffected creating a certain voltage level. This can be called X. As a sample with alcohol is introduced, some of the infrared light is absorbed. As the alcohol level increases, the amount of light passing through the chamber reaching the detector decrease. This new level of voltage can be called Y. The difference between X and Y represents the concentration of alcohol in the sample. The greater the difference between the X and Y values the higher the BAC reading.

There are other chemical structures that absorb light energy at similar wavelengths as alcohol. The chemical structures are known as “interferents,” such as acetone. The Intoxilyzer 9000 will detect a difference in the readings at the 8 and 9 micron wavelengths and will abort the test giving the message “Interference Detected”.

Easy: The Intoxilyzer 9000 isn’t perfect. It isn’t even close to perfect. Yet it is the machine that the State of Kansas has approved to be the evidentiary breath test. Regardless of how the machine actually works, if you submit to the test and your lawyer can not find a way to keep the results of that test out of court then it will be used against you. Most judges and most juries give great weight to the results of the intoxilyzer test.


Did the officer observe the proper deprivation period before he administered the test? The Intoxilyzer 8000 and 9000 require that the officer observe the person the test is being administered on for 20 minutes immediately before administering the test. The subject must be in the officer’s immediate presence and the subject must be deprived of alcohol. The officer must make sure that the person did not introduce something into their mouth in any way during that time. If the officer fails to follow this protocol this may be grounds for suppression of your breath test. (See the Intoxilyzer Protocol #1 on the appropriate model)

Was the gas used to calibrate the machine before the test from an approved gas provider? Each state has approved providers/manufacturers for the “test gas” or calibration gas. There are dozens of companies that make the gas but only a few are usually accepted by the state. If your machine was calibrated using non-approved gas, you may be able to suppress the breath test.

Was the Intoxilyzer operating correctly? Each model is different but most will have a heated tube for the suspect to blow in. The tube heater malfunctions over time. If your machine’s tube wasn’t heated properly then particulate/condensation can collect in the tube and make the machine read incorrectly. The machine will have maintenance records available. Check to see if the maintenance is up to date on the machine. If the machine is malfunctioning or has not had the proper maintenance, then you may be able to suppress the breath test.

Was the officer that administered the breath test certified on the Intoxilyzer? Before an officer can become certified to administer the breath test he/she must submit an application for “operator certification” through his/her law enforcement agency. The officer must have the written endorsement of a supervisory law enforcement officer from his agency. He or she must have completed a course of instruction on the equipment and pass a written exam. The officer then must be issued a certificate by the secretary of the Kansas Department of Health and Environment. If an officer had not met these requirements, then there may be grounds to suppress your breath test. (see page 57 of the 2023 Kansas Breath Alcohol Training Manual)

When was the officer last certified on the breath test equipment? A certificate to administer a breath test does not last forever it must be renewed. Each operator certificate issued, is at absolute most, good for two years. Each operator seeking to renew his or her certificate must submit an application to renew their certification. The operator must complete further training to keep his or her certificate. If the officer has not renewed their certification, then that will be grounds to suppress your breath test. (see page 58 of the 2023 Kansas Breath Alcohol Training Manual)

Is the agency that administered your breath test certified by the State?Before an agency can be certified by the State to have officers administer the breath test the agency must perform some tasks. The law enforcement agency “head” must submit an application for certification. The agency must prove the secretary of the Kansas Department of Health and Environment the following things. 

  • A. Specify each breath test device and provide its certification;

  • B. Maintain a roster of all certified operators who perform breath tests for that agency;

  • C. Verify that certified operators only use approved breath test devices;

  • D. Verify that each certified operator follows the devices’ protocol;

  • E. Verify that each machine is tested once per week and the results of those tests are provided to the state monthly;

  • F. Verify that the secretary has done an annual inspection of the agency

If the agency has not done these things or the agency does not renew their certification every year, then there may be grounds to suppress your breath test. (see page 56 of the 2023 Kansas Breath Alcohol Training Manual)

Was the Intoxilyzer approved by the State and are its maintenance records up to date? Each breath test machine must be certified for use by the Secretary of the Kansas Department of Health and Environment. Before that can occur the law enforcement agency must submit an application and certify that the agency intends to use the device for breath alcohol testing. The device must meet the National Highway Traffic Safety Administration guidelines and performance criteria. The continued maintenance of the device must be in accordance with the Secretary’s guidelines. The device if in need of repairs must be repaired by the manufacturer or the manufacturer’s authorized repair service. The device is not authorized if it is modified in any way that affects the operating software or alters the accuracy or precision of the device. If the device is not approved or its maintenance records up-to-date then this may be grounds to suppress your breath test results. (see page 59 of the 2016 Kansas Breath Alcohol Training Manual)

Did the External Standard Check results fall within the acceptable range? The standard range is 0.075 to 0.085 on both the Intoxilyzer 8000 and Intoxilyzer 9000. If the standard check was not within the acceptable range this is a grounds to suppress the results of your breath test. (see the Intoxilyzer Protocol on the appropriate model, #5)

Did the Law Enforcement Agency maintain the proper records? Each agency custodian must maintain records for three years on each Intoxilyzer that is in service under that agency’s control. The agency must maintain records of all officers that are certified to use the machines, they must maintain maintenance records for each of the machines and they must maintain records showing that a quality control check was completed at least once each week for each intoxilyzer device assigned to that agency. Failure to maintain the proper records can be grounds to suppress the breath test. (see page 59 of the 2023 Kansas Breath Alcohol Training Manual)

Was the Intoxilyzer affected by Radio Frequency Interference? The intoxilyzer is a sensitive instrument and it is susceptible to interference. One of the problems with the intoxilyzer is radio interference. The radio frequency emitted by a cell phone or a police radio can cause the test to malfunction. Although the system claims to have automatic detection or radio frequency interference, it is not full proof. If an officer was communicating on the radio or a cell phone during the administration of the test, the results may have been affected by radio interference. If your test was affected by Radio Frequency Interference you may have grounds for suppression. (see page 85 of the 2023 Kansas Breath Alcohol Training Manual)

Did the officer use an unused mouth piece on the Intoxilyzer before you took the test? The intoxilyzer has a specific protocol for administering the breath alcohol test. If the protocol is not followed exactly then the test results may be affected. Each testing subject must use a clean unused mouthpiece when they submit to the test. If an old or used mouthpiece is used during the test, then the results may be affected. If you did not see the officer install a new mouth piece before you submitted to the intoxilyzer test, then you may have grounds to suppress the results of that test. (see the Intoxilyzer Protocol on the appropriate model, #6)

Did the officer read the Advisory before administering the Breath test? An officer is required to read aloud the DC-70 Advisory to a person suspected of driving under the influence if the officer intends to have the person submit to a breath alcohol test. If the officer fails to read the advisory it may be grounds to suppress the results of the breath test. (see pages 8-14 of the 2023 Kansas Breath Alcohol Training Manual)