Intoxilizer EC/IR II Breathalyzer

The Intoxilizer EC/IR II is a machine, not an instrument, created by Intoximeters, Inc.  The designation as an “evidentiary” machine simply means the machine meets certain standards set forth by the National Highway Traffic Safety Administration (NHTSA) and in turn, permits the test results to be used against a person in court proceedings. Further, it is the breath testing machine approved by the North Carolina Department of Health and Human Services for use by law enforcement agencies in North Carolina.  

The Intoxilizer EC/IR II is said to employ two different testing methods for determining alcohol content in an individual’s breath sample:  infrared analysis and fuel cell testing.  Each method will be discussed in greater detail below.

Infrared Analysis

The infrared (IR) analysis is the first method by which a person’s breath is analyzed to determine the alcohol content.  The infrared (IR) analysis is continuous while a breath test is being provided to the machine. When a breath sample is introduced into the machine, the breath is directed through the blow tube and then into a sample chamber.  On one end of the sample chamber is a light source.  The light source emits a broad spectrum of wavelengths of infrared light.  The light waves are focused on a spinning dial containing filters.  

Particles of the light are then absorbed by compounds in the breath.  Ethanol is the type of alcohol found in alcoholic beverages.  The light that is not absorbed by the ethanol and other compounds in the breath molecules continue to the filter wheel.  The wheel is set up with filters that modulate, or filter, the wavelengths that arrive at the detector.  The dominant wavelength to reach the detector is the wavelength at which ethanol absorbs light.  Secondary wavelengths are those of other substances that may be found in the breath and, if detected in concentrations, would adversely effect the machines ability to detect alcohol concentrations.  

After passing through the filter wheel, the light then reaches the infrared detector.  The detector has two channels: one for ethanol and one for carbon dioxide.  The amount of light that reaches the detector is compared to that which was initially put out from the light source. The detector is connected to a microprocessor.  The microprocessor then uses a particular algorithm, or specific computer code unique to the manufacturer, to determine the amount of alcohol present in the breath sample by comparing the amount of light that reaches the detector compared to that which was known to have been put out by the light source.

Sufficient Volume and Flow of Breath

Attached to the tube in which the breath sample enters into the IR sample chamber is a pressure sensor.  In order to be an evidentiary testing machine, according to NHTSA requirements, a machine must accept a minimum of 1.1 liters of breath.  Each state may require a larger breath sample but states are not permitted to allow less than the minimum breath quantity.  Once the minimum amount of breath has been provided to the machine, the IR system will monitor when the breath starts to weaken in intensity.  Once the flow drops a certain percentage, the machine draws a small portion of the breath sample from the IR sample chamber into the fuel cell.

Fuel Cell

While the infrared detection system is continuously monitoring a breath sample, the fuel cell only analyses 1 cc of air, or 1/1000th of the minimum amount of breath that is required for a valid breath sample.  The breath sample enters the fuel cell by a port located in the top of the plastic in which the fuel cell is located.  The fuel cell itself is coated on either side with platinum black, which is used as a catalyst and and for absorbing gases.  Inside the coating is a porous, chemically inert disk that is impregnated with an acidic electrolyte solution.  It is within this solution where the breath sample will create a chemical reaction when alcohol is present.  Attached to the black coating on either side is an electrical connection that attaches to the microprocessor.  

When the breath sample enters into the porous disk, a chemical reaction occurs which in turn creates an electrical charge.  First, the alcohol molecules convert to acetic acid.  This chemical reaction to the presence of ethanol creates an imbalance between the upper and lower portions of the disc.  This imbalance occurs when alcohol enters the fuel cell, the chemical reaction produces a fixed number of electrons per molecule of alcohol introduced into it.  Further, the conversion to acetic acid also releases certain hydrogen (h+) atoms from the ethanol compound.  The released hydrogen atoms move to the lower portion of the disc where they combine with oxygen.  This new combination consumes one electron per hydrogen molecule.   Therefore, the imbalance is extra electrons in the upper portion of the disc and a reduction of electrons in the lower portion of the disc.  This imbalance creates a current in order to neutralize the imbalance, and the current flows out of the cell through the electrical connections attached to the disc.  A larger quantity of alcohol in the breath sample will create a stronger current. Therefore, the current released from the fuel cell is directly proportional to the alcohol content of the breath sample.  The microprocessor will then convert the current to the test results displayed on the machine.

Purging the Breath Tube

The Intoxilizer EC/IR II is set up to run self checks prior to taking an individual’s breath sample, as well as in between an individual’s breath samples.  These checks are called air blanks and are intended to ensure there is no residual alcohol in the machine. The air blank, or purging function, is accomplished by a purging fan.  The fan draws room air into the machine through the breath tube.  The purge then clears out the air in the sample chamber and forces it out of the machine through an exhaust port.  

Challenges to Breath Testing Principles

After being armed with some basic knowledge about the machine that will provide evidence to convict a person in criminal court, it is important to learn more about the science behind how the machine comes to its conclusions.  The following information will contain several issues that have, or are, being addressed concerning the governments position on breath testing principles and whether or not the machines are accurate enough to be considered evidential.  

Partition Ratio

The results from breath testing is considered as representative of a person’s blood alcohol concentration (BAC).  In order to compare the results of a breath test to the actual alcohol concentration in a person’s blood, one must look back to the inception of breath testing.   In 1938, a university biochemistry and pharmacology professor determined that 2100 milliliters of deep lung air, also known as alveolar air, contain the same concentration of alcohol as one milliliter of arterial blood.  Thus the 2100:1 partition ratio was born.  This has been accepted widely by courts and breath machines are set up in accordance to this standard.  

However, some in the scientific and legal communities now question whether this ratio is accurate.  It is argued that the ratio is closer to 2300:1for the average population.  The new ratio means that breath machines are over calculating blood alcohol concentration because they do not take into account the larger disparity between breath and blood alcohol concentration.  Meanwhile, courts continue to accept the 2100:1 ratio, ignoring the fact that the ratio may be inaccurate.  Furthermore, according to one report, the 2300:1 ratio only represents around eighty percent of the population, meaning that for twenty percent of individuals tested on a breath machine, the results will be much more inaccurate.

Slope Detectors and Mouth Alcohol

The Intoxilizer EC/IR II contains a slope detector that is meant to detect the presence of mouth alcohol in a breath sample.  If the ethanol concentration has a negative slope, or quickly declines, throughout the breath sample, this is an indication that the presence of mouth alcohol, instead of deep lung air. In order for a breath sample to be representative of the blood alcohol concentration, it must contain alveolar air.  The alveoli are located within the lungs, and are the point at which gases are exchanged between the blood and lungs.  While the carbon dioxide is transferred from the blood to the lungs, other gasses, like ethanol, are also transferred to the lungs.  The gasses are then expelled from the lungs when the person exhales his or her breath.  

While performing a breath test, a person is required to exhale for an extended period.  It is the latter end of this exhalation that will contain mostly air from the alveoli sacs and be most representative of the persons blood alcohol concentration.  However, alcohol is also found in the soft tissue of the mouth, throat and upper lungs and added to the breath that is exhaled.  For this reason, law enforcement is required to perform a fifteen-minute observation period to ensure that any alcohol that is present in the mouth, throat and upper lungs has time to evaporate.  This observation period is said to ensure the test is performed with alveolar air, making it a true representation of the blood alcohol concentration.  

Observation Period and GERD

Although the observation does clear the oral cavity of alcohol already present, it does not guarantee that new alcohol may not be introduced.  During the observation period, the person is instructed not to burp, belch, or vomit during the observation period.  If any of these occur, the observation period must be started again because of the potential for introducing alcohol back into the mouth and throat. One bodily function that law enforcement cannot detect, however, is acid reflux, or gastro esophageal reflux disease (GERD).  GERD events occur when stomach contents, including gases, enter the esophagus and oral cavity.  This introduction may not be detected by the slope detector.   

Pre-Absorption BAC v Post-Absorption BAC

When a person consumes alcohol, it takes time for the body to absorb and eliminate the alcohol.  While the body is absorbing the alcohol, the person’s BAC and breath alcohol concentration are starkly different.  The amount of time this absorption takes is dependent on the quantity of alcohol consumed, the quantity of food in the stomach, body composition, and gender.  Studies have shown the absorption process can take up to 166 minutes from the end of alcohol intake.  During this absorption period, breath alcohol concentrations have been shown to be as much as one hundred percent higher than that of the blood alcohol concentration.  

Specificity for Alcohol

A person’s breath can contain hundreds of different compounds.  Even manufacturers admit that there is a possibility of cross reactivity with other substances that are found in the breath.  Further, ethanol is just one compound found in the alcohol family that contains the methyl group, a part of the ethyl alcohol compound.  However, the machine cannot distinguish from which of the many ethyl alcohol substances the methyl group was contained in. In addition, many other substances can absorb infrared light, even in the same wavelength as ethanol.  The combination of ethanol with these other compounds can lead to an elevated reading on the breath machine.

Radio Frequency Interference (RFI) Detectors

Evidential breath testing machines utilizes electrical circuits to perform its different functions and determine results of different functions.  Because many of these functions are electrical processes, they are susceptible to interference by other electrical components in close proximity.  Objects like radios, cell phones, or other electrical devices that are within close proximity to a breath testing machine could interfere with the proper function of the machine, leading to incorrect test results.  

Although most machines are equipped with radio frequency detectors, if they are not set to detect the actual frequency at which other electronic devices are functioning, then the detector will not be able to acknowledge the interference and abort the testing process when necessary.  Further, the number of electronic devices that are found in a law enforcement office, in addition to the breath testing machine, is staggering when you think about the number of stationary radios, hand-held radios, computers, recording devices, and audio visual equipment.  If any of these are located in close proximity to the breath testing machine, and the RFI detector is not adequately set up to detect all frequencies above a RFI free environment, then it is very likely that many of the test results have been affected by such interferences.  

Body Temperature and Test Results

One of the greatest problems with breath testing machines is they assume an exhaled breath temperature of thirty-four degrees Celsius (93.2 degrees Fahrenheit).  The problem with this assumption is that even a slight variance, even one degree, can cause a person’s BAC to be reported with an increase of a minimum of seven percent.  That increase could be enough to cause a person’s test results to cross over the .08 limit and lead them to being arrested, when in fact their actual blood alcohol concentration was below the legal limit.

Although a simple solution might be to including the means of measuring breath temperature to the machine, most manufacturers do not.  In particular, the Intoxilizer EC/IR II does not have the ability to monitor actual breath temperatures.  The failure of manufacturers to account for variances in breath temperature can lead to many individuals being improperly arrested.  

Dry Gas Issues

When the Intoxilizer EC/IR II performs its internal checks, it uses a dry gas solution.  The self check is performed by drawing from a tank containing ethanol and nitrogen.  The nitrogen does not absorb any of the infrared light, therefore, the reading of the internal check is only based on the ethanol when the machine is calibrated. The problem arises when a person is being tested on the machine.  The difference between the self test and the human test, is that a human breath sample contains moisture and therefore, affects the readings more than the dry gas during calibration.  During a self test, the only substance absorbing infrared light is the ethanol; during a human test, there are other substances, in addition to the ethanol, that are absorbing infrared light.  More substances absorbing infrared light means higher test results.