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How Does a Breathalyzer Work? (And Should You Refuse One?)

Before you actually make a decision to provide a breath sample or refuse one, you should know what a breathalyzer is and what it does. In Montana, law enforcement use two different types of breath alcohol analyzing machines, or breathalyzers, if they suspect you of a DUI. In a police cruiser, law enforcement use a small, hand-held device commonly known as a Portable Breath Test, PBT, or Preliminary Alcohol Screening Test. The device looks like this:


So how does a breathalyzer work? A PBT device reads out a measurement of your breath’s deep lung alcohol concentration. Most people believe these machines are testing their blood alcohol, but in reality they are testing your breath alcohol.

The machine is designed to test a certain sample of air. Law enforcement is trained to have you blow through the disposable tube for several seconds, until you’re almost out of air in your lungs. The tube is hollow, so the breath blows through it.

However, there is a very small part of the tube that is an inlet into the PBT machine. When you have exhaled through the tube for several seconds, you’re beginning to exhale what is called deep lung air. This is believed to give a more accurate sample of what a true blood alcohol reading would be, as it is the alveoli air that is exchanging oxygen with the blood that is being exhaled. At that point, the officer depresses the “Set” button, which will allow the machine to capture a sample of that air running through the tube and be tested.

Let’s get technical for a second. PBT machines work on the science of a fuel cell. This type of fuel cell is an electrochemical sensor that reacts with alcohol. The reaction of alcohol with the fuel cell generates a number result that is shown on the display. Essentially, the more alcohol that reacts with the fuel cell, the higher the reading.

breathalyzer test

Source: KOMU News

Can a Breathalyzer Fail?

There are many factors that can cast doubt upon the breathalyzer’s reading. First, a breathalyzer must be constantly calibrated to ensure the fuel cell is reading correctly.

Law enforcement officers test breathalyzers by introducing a test gas with a known alcohol value so they know what the reading should be. If the PBT is not reading out the correct number of the test gas, it can be adjusted with a manual screw adjustment. The fact that this machine can be adjusted by hand and needs adjustment at times shows that fuel cells can degrade over time and become unreliable.

In addition, law enforcement must wait 15 minutes from when they first encounter a subject before obtaining a breath sample. This is because any residual alcohol in the mouth can affect the reading. For example, if you used mouthwash just before getting pulled over for a potential DUI and taking a breathalyzer test, the readout would be affected because mouthwash has alcohol in it. The industry standard seems to be a 15-minute wait to declare that any possible mouth alcohol would be gone and absorbed by the body prior to testing.

Breathalyzers at the Police Station

A breathalyzer at a police station is different from the one law enforcement officers have on the road. It’s a much larger and more advanced machine that also measures breath alcohol. Here’s what it looks like:

breathalyzer machine

In Montana, most agencies use the Intoxilyzer 8000 manufactured by CMI Inc. This machine weighs almost 18 pounds and has a variety of improvements over the PBT. The Intoxilyzer 8000 analyzes alcohol using infrared spectroscopy, rather than the somewhat archaic fuel cell method of the PBT.

Without giving a science lesson, infrared spectroscopy is where infrared light passes through a sample of your breath. This breath is also deep lung air, just like with the PBT. Any alcohol molecules in your breath sample will actually absorb some of the radiation of the infrared light. The machine measures the amount of infrared radiation that hits the other side of the chamber against the amount that was started with, and the difference is a measurable amount of alcohol molecules that were present in the sample.

Don’t Try to Beat a Breathalyzer at the Station

The Intozilyzer 8000 is also more advanced than the PBT in that it allows the law enforcement operator to determine if the subject is actually blowing air into the machine. This breathalyzer tells the operator exactly when enough breath has been blown to obtain deep lung air, and the result is printed out on a paper, not just displayed on an LED display.

Often someone will try to “beat” a breathalyzer by blocking the machine’s straw with their tongue, or blowing air out between their cheeks and the straw. The Intoxilyzer 8000 actually has an audible buzzer that indicates when a proper breath sample is being blown into it. So if you’re trying to beat the machine, it will tell the operator what you are doing. The machine also determines when deep lung air is achieved and takes the sample itself, instead of the officer pressing a button, as with the PBT. Essentially, the Intoxilyzer 8000 takes the human error out of the equation and allows the breathalyzer to do almost everything.

So Should You Take a Breathalyzer Test?

In Montana, several cities including Missoula have enacted laws that make it a misdemeanor crime to refuse breath tests. Private criminal defense attorneys in Missoula, MT will typically tell you that if you drank more than 1 alcoholic beverage per hour, you are likely near or over .08, and you should refuse a breath test if pulled over for DUI.

passed breathalyzer

Image: Janet Lackey

What advantages are there to providing a breath test or refusing a breath test? If you provide a breath test, there is really no advantage to you. If your breath alcohol is below .08, you can still be charged with a DUI. It is very rare for an officer to “unarrest” someone for DUI if they provide a breath sample below the limit. Often times, the officer thinks someone is also under the influence of drugs, and that combination is also illegal and falls under the DUI laws of Montana. In reality, there is no advantage to taking a breathalyzer test as far as prevailing in a DUI charge is concerned.

Refusing a Breathalyzer Test

The advantage in refusing a breathalyzer is simple: There’s less observable evidence against you, should you have a criminal jury trial to determine your guilt. I can tell you as a former prosecutor who has tried numerous DUI trials before jurors: Once a juror sees the breath alcohol concentration, and it is above .08, they just roll their eyes and wonder why they are even there. Then they convict you.

Breathalyzer results are simply too compelling of evidence to overcome at a trial. However, if there is no breathalyzer evidence in numerical form, prosecutors have a much more difficult time proving guilt beyond a reasonable doubt that a driver was under the influence. Prosecutors are stuck with evidence of field sobriety testing and a video of how the accused performed those tests. That evidence is much easier for a criminal defense attorney to argue before a jury and gives you a better chance for a not guilty verdict.

In the end, if you have honestly had less than 1 drink per hour, then you should consider taking a breathalyzer test, as you are not likely to be over the limit. However, 1 drink per hour is somewhat uncommon, and the average person that is drinking alcohol is drinking more than that amount. If you drink more than 1 drink per hour, your chances of being over the limit are too close to risk.

Have you ever taken a breath test? Have other questions? Leave them in the comments below and we’ll answer them, or contact one of our attorneys at the Judnich Law Office for a free consultation.


Need a Family Law Attorney in Missoula, MT?

divorce decree papers

When it comes to family, emotions run high. Family law, divorce and child custody are some of the most delicate cases due to their deeply personal nature. At the Judnich Law Office, we handle all family law clients with discretion, care, and sensitivity — and above all, knowledge of the law that can help you win your case.

Why Hire a Family Law Attorney?

No one plans on getting divorced or battling over child custody. Thus you may be unfamiliar with current laws and requirements surrounding child support, divorce, and legal separation. Our family law attorney knows exactly what paperwork must be completed to make things official and get all that belongs to you.

At the Judnich Law Office, we negotiate for you so things remain civil. With tensions and defenses up, a family law attorney is not only a much-needed legal expert and skilled arbitrator, but an unrelated third party who can help calm things down when necessary. In addition, a Missoula divorce lawyer can come to your aid if your spouse is attempting to hide assets during the divorce or otherwise preventing the equitable split of resources (defined as a division of property that is fair but not necessarily equal).

Family Law Practice Areas

Our Missoula divorce attorney is highly skilled and experienced in the following areas:

  • Divorce
  • Annulment
  • Legal Separation
  • Domestic Disputes
  • Restraining Orders
  • Marital Agreements
  • Prenups
  • Child Custody
  • Paternity
  • Guardianship
  • Adoption
  • Name Changes
  • Other Issues

More details about these family law areas follow.


Up until the late 1960s, you could not get a divorce without proving one spouse did something wrong. Now Montana and all other states offer “no-fault divorce,” which means you do not have to prove that your partner caused the marriage to dissolve. (Heard the term “irreconcilable differences”? No-fault celebrity divorces brought it into the lexicon.)

Judnich Law Office’s divorce attorney will help settle your marital split, even if it is an abandonment divorce, adultery divorce, or military divorce. To get a divorce in Montana, you or your spouse must have lived in-state for at least 90 days, and you must attest that either your marriage is beyond repair or you and your partner have lived apart for 180 days. After that, the court will provide you with a “dissolution of marriage.” A Missoula divorce attorney will help with the difficult process of dividing your assets, house, 401k, and other shared resources.

signing divorce paperwork

Domestic Disputes

As the Montana Department of Justice writes, “It is against the law for a partner or family member to cause you bodily harm or cause you to fear bodily harm.” Judnich Law Office’s family law attorney will assist you with cases related to domestic violence, sexual assault, stalking, intimidation, and elder abuse. Abuse is not always physical — financial, emotional, verbal, or written abuse can also be grounds for a restraining order, or what in Montana is called an Order of Protection. We take any instance of abuse, threats, or harassment very seriously and will fight for your protection. The most important thing is your safety. Similarly, if you are accused of domestic violence or abuse, expert legal representation is a must.

Marital Agreements

Marriage can be not only a legal distinction but a major life change. Our Missoula family law attorney can help you draw up a prenuptial agreement to ensure assets are divided fairly should the marriage dissolve. Civil unions are also within our expertise. As of October 2014, same-sex couples can register in Missoula as domestic partners. The Judnich Law Office can advise you on the legal issues related to registering or dissolving your domestic partnership.

The family law attorney can also assist you with legal separations and annulments. Filing for a legal separation means a married couple will live separately yet remain married. In Montana, a legal separation may be converted to a divorce after six months.

An annulment is a complicated and often misunderstood process. In fact, Montana no longer calls it an annulment at all, but a “declaration of invalidity.” And it is not for short-lived marriages but those involving a minor, relative, someone mentally incapacitated, or someone under the influence of alcohol or drugs at the time. If you need an annulment, contacting a Missoula divorce lawyer is the first step.

baby feet child custody

Photo: Christine Szeto


Separating couples in our office are often most worried about the custody and welfare of their children. A skilled Missoula child custody lawyer will help you navigate visitation, sole custody, child support, and more. You and your partner will create a parenting plan to submit to the judge that explains where your child will live, who will make the main decisions about education, what each parent will contribute financially, visitation rights, and what will happen if the parenting plan is violated. Child custody lawyers will guide you through the process of creating a parenting plan, as well as establishing or challenging child custody, child support, and visitation rights.

We can also assist you with issues surrounding paternity. Our family law attorney will guide you through legally establishing paternity or determining paternity via genetic testing. Once blood and/or DNA tests identify the father, he may have visitation rights or be required to financially contribute to the child’s upbringing.

Our family law attorney will also aid you in adoption and guardianship cases. Step-parent adoption may be desired if a mother is married to someone other than the child’s father or was unmarried when the baby was born. The Judnich Law Office also regularly deals with guardianship cases, including legal guardianship, grandparents’ rights, Guardian ad Litem (court-appointed guardian) services, and representation of parents in state child custody (Department of Family Services) cases. No one should unlawfully keep you from your child or grandchild.

Name Changes and Other Family Law Issues

Changing your name after a marriage or divorce can seem like a daunting ordeal. You’re required to notify the state and Motor Vehicle Division, file a petition for name change, attend a court hearing in some cases, and then change your driver’s license, title, registration, and possibly Social Security card (not to mention banking cards). Thankfully, the Judnich Law Office’s family law attorney can expedite the process so your life can begin with your new name.

legal name change form

Photo: Heather Quintal

Family Law Terms to Know

We at Judnich Law Office do our best to make the legal process easy to understand. However, the legal jargon surrounding family law cases is often confusing. Here are several terms you may hear during the resolution of your case:

  • Contempt: If someone can but refuses to comply with a legal agreement, he or she is in contempt of court and may be fined or even jailed. The Judnich Law Office can represent you if you are found to be in contempt during a family law matter.
  • Mediation: To save money and prevent taking a divorce to court, a couple may use mediation to resolve disagreements. This involves both partners coming to a solution with the help of a third party. Lawyers may or may not participate in mediation.
  • Modification of Judgment: After a judge has handed down a decision about your child support or custody case, a modification of judgment may occur if there are “substantial changes in circumstance,” such as someone getting fired.
  • Maintenance: This is the current term for alimony or spousal support. A court will order maintenance if one partner in the divorce is unable to provide for her- or himself. The length of the marriage, partners’ health and age, and any children are factors in the decision.

Why Choose the Judnich Law Office?

Family law matters such as divorce and adoption can be overwhelming. Endless paperwork and court appearances are the last thing you need during this stressful time. Partnering with the Missoula family law attorney at Judnich Law means you can focus more on your family and personal life rather than trying to become a legal expert overnight. Whether your case is straightforward or complicated, we at Judnich Law bring the legal background, years of family law expertise, and negotiation skills to achieve the desired result in or out of court.

Get Your Questions Answered at No Charge

It starts with a consultation. We want to learn everything about your situation so we can chart a course seeking the most desirable outcome for you. Call (855) 853.1482 for your Free, No Obligation Phone Consultation today.


Divorce and Family Law related representation


The Judnich Law Office is happy to offer our clients representation services in family law matters. Our firm has added attorney Lucy Hansen to our team, and she brings with her a wealth of knowledge in all family law matters ranging from her time as a solo attorney handling family law cases, to her exceptional experience as an Assistant Attorney General for the State of Montana  in the Child Protection Unit. Lucy offers free consultations in family law matters ranging from annulment, divorce/dissolution of marriage, legal separation, domestic disputes, restraining orders/orders of protection, prenuptial agreements, child custody/parenting, paternity, adoption, legal name changes, legal guardianship, grandparents’ rights, step-parent adoptions, Guardian ad Litem investigations and reports, and representing individuals in state child custody DFS cases (Department of Family Services).

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Judnich Law Office | 2419 Mullan Road Missoula, MT 59808 | Phone: (406) 721-3354

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