Fuel cells are a hot topic among environmentally friendly engineers, but they are also being used to sniff out the boozy breath of intoxicated drivers.
Law enforcement agencies in Santa Barbara have recently begun using a new type of breath sensor that uses fuel cell technology to determine the alcohol content of breath samples. This sensor is portable – a big change from previous systems, which required a trip to the jail for testing.
A fuel cell is a device that combines fuel with oxygen to produce electricity. This process contrasts combustion in which fuel is burned with oxygen and produces heat.
The fuel cell used in the Alcotest is built around a thin plastic membrane that separates an anode and a cathode where hydrogen and oxygen are introduced, respectively. Another device, called a reformer, changes the incoming ethanol molecules into its constituents: Hydrogen and oxygen are used in the fuel cell, and carbon is discarded as carbon dioxide.
The hydrogen reacts in the presence of a platinum catalyst. This causes the hydrogen to split into protons and electrons. The protons are allowed to pass through the membrane, but the electrons are not.
On the other side of the membrane, oxygen molecules are also reacting in the presence of platinum and have received the protons from the hydrogen side of the membrane.
The electrons that were created on the hydrogen side are compelled by an electric attraction to also reach the oxygen side. They are not allowed to pass through the membrane, so they must move through an external circuit. The flow of electrons indicates how much fuel is flowing through the cell.
The New Sensor
The new sensor is an Alcotest 7410 developed by DrS
The Goleta Traffic Bureau has four Alcotest devices. Three of the units are carried with officers on patrol and the other unit remains at the jail. All of the devices arrived the week of New Year’s Eve, when the Sheriff’s Dept. made four arrests using them.
The Dept. of Justice provided the units for free to the Goleta Traffic Bureau from a federal grant. The Alcotest 7410 kit normally retails for $2,500.
The Isla Vista Foot Patrol does not have any of the new units yet, but are expecting them soon. The devices are becoming standard among all law enforcement agencies in the state. The local California Highway Patrol office has three but was unable to provide any information about their use.
The new technology allows portable devices to be accurate enough to be used as evidence in court. To use stationary devices, police have to take suspects to jail for testing, said Sheriff’s Dept. Deputy George DeLuca.
“Suppose you blew into this device now, and blew an 0.08. If you hadn’t been drinking for a while, your blood alcohol level would be declining,” DeLuca said. “So, it’s important for us to get the breath test done relatively soon to make sure we still get you in that 0.08 range. Since this device is an evidentiary test out in the field, no need to rush you anywhere.”
Before this sensor was available, the officer’s only option was to take the suspect to the jail for blood or breath testing at a stationary unit. Suspects who were just above the BAC limit of 0.08 when pulled over might sober up to just below the legal limit by the time they arrive at the jail. This posed many problems for officers proving a suspect’s BAC in court.
In addition to the benefit of instant testing, the new portable sensor also makes it easier for the officer to enter information about himself and the driver.
“You’ve got a user ID card that’s specific to [each officer],” DeLuca said. “You swipe the card, now it knows who you are. Now it’s going to say, ‘Do you have a driver’s license to swipe?'”
The driver’s name, address, and license number are recorded when the card is swiped and the officer does not need to type it in.
DeLuca said that the device is useful in cases where a drunk driver crashes and is too shaken to perform a field sobriety test, such as walking on a straight line or touching his or her nose.
“At the scene of the accident, you blow into this thing a couple times,” DeLuca said. “The paramedics scoop you off, I got my 0.10 test results – it’s just a much smoother process.”
In the past, if a driver involved in an accident was suspected of being drunk, the driver was taken to the hospital where the police could not perform an intoxication test. The law enforcement agency would have to subpoena blood test results from the hospital if needed for a court case.
Alcohol is a general type of chemical compound that encompasses hydrocarbon molecules with one or more hydrogen atoms replaced by an oxygen atom and a hydrogen atom. Ethanol (ethyl alcohol) is a specific alcohol that has two carbon atoms.
Ethanol is infinitely soluble in water, meaning it mixes and doesn’t separate out like oil and water. This property – as well as the fact that it is not very toxic – makes ethanol the choice for all alcoholic drinks. Methanol is another specific alcohol that is cheaper to make than ethanol, but is very toxic. It is used in motor fuels and laboratories.
There are many other alcohols, each with a different number of carbon or oxygen atoms. They all have different properties, but ethanol is always the ingredient in drinks that makes them alcoholic.
Alcohol in the Body
Alcohol molecules are different than most food and drink molecules because they can pass into the blood without being processed by the digestion system.
For example, after eating a hamburger, the stomach takes time to digest the beef into its constituent amino and fatty acids, which then enter the blood. Alcohol is able to enter the blood directly through the mouth, stomach and small intestine where it remains chemically unchanged in its composition from when it was swallowed.
Alcohol will be absorbed into the blood more quickly if the stomach happens to be empty. This is because the valve that connects the stomach to the small intestine is not closed, and the alcohol can enter the small intestine, which leads to very rapid absorption. If the stomach is busy digesting a lot of food, the valve will be closed and the alcohol cannot proceed to the small intestine as quickly.
Once the alcohol reaches the bloodstream, it takes less than two minutes to reach the brain and affect the central nervous system. Alcohol is also a diuretic, meaning that it causes the body to lose water through urination.
The liver breaks down 90 percent of consumed alcohol into other chemicals that the body stores. Five percent is exhaled in the breath and 5 percent is excreted in the urine. These three methods of removal allow the average person to eliminate 14 grams of ethanol per hour. Twelve ounces of beer, five ounces of wine, or 1.5 ounces of hard liquor all have about 14 grams of ethanol in them, so the average person eliminates one drink per hour.
Blood alcohol concentration is a ratio that describes how many grams of alcohol are present in 100 milliliters of blood. If a person consumes alcohol at a rate faster than their body can eliminate, the extra alcohol will be stored in the bloodstream, leading to a higher BAC.
Not everyone’s BAC will vary the same amount after having the same amount of alcohol. Heavier people have more blood, so the same amount of alcohol will be more dilute in their bloodstream. Women have proportionally more body fat than men, and alcohol is not readily absorbed into fat. Thus, a woman will have a higher BAC than a man of the same weight after having the same amount to drink.
It is possible to chemically test for the amount of alcohol in a blood sample, but there is a faster, less invasive way.
Alcohol is a very volatile substance, which means that it evaporates quickly. It is much easier to smell an open bottle of vodka than it is to smell an open bottle of milk because the vodka is more volatile. More molecules are evaporating out the top of the bottle, through the air and into the nose.
Alcohol in consumed beverages quickly enters the bloodstream, where it circulates in its original form.
As alcohol in the bloodstream passes through the lungs, a portion of the alcohol evaporates into the air in the lungs and is exhaled out of the body. The amount of alcohol this exhaled is proportional to the amount in the blood. This allows a device to measure the alcohol in someone’s breath and calculate their BAC.
Out With the Old
The first alcohol breath sensors consisted of a small glass vial filled with a chemical solution. The person suspected of drinking blows into the glass vial and the solution changes color due to a chemical reaction with the alcohol in the breath sample.
Some devices use an electronic monitoring system to detect and quantify the color change, thus delivering a definite BAC level.
The next type of breath sensor to be widely used employs a method called infrared spectroscopy to detect alcohol. The sensor is known as the Intoxilyzer 5000. This system operates by shining an infrared light through the breath sample and detecting any reduction in the light that passes through it.
This is similar to the way in which a person can tell how much pollution is in the air by looking off into the distance and noting the brownish color.
This new application of fuel cell technology will allow law enforcement officers to better evaluate intoxicated drivers. It is just one way in which the popularization of fuel cells will lower their cost and encourage new development.
The alcohol-sensing application has become so popular that half a dozen companies offer hand-held and key chain units for under $50. While the accuracy of such devices may not be that great, their use may encourage people to think twice before drinking and driving.