Interlock Device vs Car Breathalyzer: What a Breathalyzer for Your Car Is and When You Need One

A breathalyzer for car ignition is an ignition interlock device, or IID: a breath tester wired into your car’s ignition that keeps the engine from starting until you give a breath sample under the limit your state sets. State interlock laws differ on who needs one and for how long. If a court or your DMV requires one after a DUI, the car breathalyzer you’ll have installed is this device.

With all the requirements and terms, it can quickly become confusing, especially because there are quite a few names for these drunk driving prevention devices. A handheld tester you keep in the glove box, or a device you buy on your own, is a different product, and neither one satisfies a court or DMV requirement.

What Does “Breathalyzer for Car” Mean?

When people search for a breathalyzer for car use, they usually mean one of three things. Only the first one counts toward a court order or a DMV requirement.

• A court-ordered ignition interlock. A certified device leased from a state-approved provider, installed by a technician, calibrated on your state’s schedule, with results reported to the authority monitoring your case.
• A voluntary in-car device. A breath tester that also connects to the ignition, bought privately (for example, by a parent of a new driver or an employer with a fleet). It isn’t part of a state program, and nobody reviews its results except the person who set it up.
• A handheld personal breathalyzer. A pocket or glove-box tester that estimates your breath alcohol. It doesn’t connect to the car and can’t stop the engine from starting.

If you’re here because a judge or the DMV told you to get a car breathalyzer, you need the first kind, installed by a provider your state approves.

Interlock Device vs Car Breathalyzer: Same Device, Different Names

“Breathalyzer” has become an everyday word for any device that estimates blood alcohol concentration from a breath sample. People use it for the handheld unit police carry at a traffic stop and for the device that keeps an impaired driver from starting a car. When you hear “interlock device” or “car breathalyzer,” though, both names refer to the same thing.

Common names for an IID include:

• Alcohol ignition interlock
• Breath alcohol ignition interlock device
• Car breathalyzer
• Ignition interlock device
• IID
• In-car breathalyzer
• Ignition interlock
• Interlock
• Interlock device

Court papers and state forms often use BAIID, short for breath alcohol ignition interlock device. Our glossary of interlock acronyms lists the rest.

What Is an Ignition Interlock Device?

An ignition interlock device is a breathalyzer connected to your car’s starting system, so the engine only starts after a passing breath test. It combines two parts:

• A breathalyzer. It measures the alcohol in a sample of deep-lung breath and uses it to estimate your blood alcohol concentration (BAC).
• An immobilizer. An electronic switch connected to the ignition that keeps the engine from starting until it receives a pass signal.

Interlocks exist because impaired driving is common. In 2012, an estimated 4.2 million U.S. adults reported driving while impaired by alcohol at least once in the previous 30 days, which added up to about 121 million impaired-driving episodes that year. Courts and state programs use alcohol ignition interlocks to separate drinking from driving for people with an alcohol-related offense, and the device grew out of the breath testers police first used decades ago.

What Does a Breathalyzer in a Car Look Like?

A breathalyzer in a car usually looks like a small handheld unit with a mouthpiece and a screen, connected by a cord to a control box mounted out of sight under the dashboard. In the states where Low Cost Interlock offers the 777, the handheld can sit inside the Interlock Can, a cover that fits over the 777 and looks like a soda can.

When Is a Car Breathalyzer Required?

A car breathalyzer is required when a court orders one as part of a DUI case or when your state DMV makes one a condition of driving again. Which offenses trigger it, how long it stays in the car, and whether it comes with a restricted license all depend on the state and on the facts of your case, so the court order or DMV notice is the document to follow.

Some states issue a restricted license that lets you drive only with an interlock installed, such as an ignition interlock limited license. The name and rules for that license vary by state, and your DMV can tell you whether one applies to you.

Two points often get confused:

• A voluntary device doesn’t count. A breathalyzer you bought yourself isn’t a certified interlock, and its results don’t reach a court or DMV.
• The install follows the order. An interlock is installed once a court or DMV requires it. Installing one before an order exists doesn’t count toward a requirement or shorten one. If your case is still open, ask your attorney whether an interlock is relevant to it.

What a Court-Ordered Car Breathalyzer Involves

If you’ve been mandated by law to install an IID in your vehicle, you may be curious about what that entails and what’s required of you. Depending on your state, the steps usually include:

• Getting the right license. If your license was suspended or revoked, your state may require you to apply for a restricted or interlock license that allows you to drive only a vehicle with an interlock.
• Leasing a certified device. You lease the interlock from a state-approved provider such as Low Cost Interlock, and a certified technician installs it. You pay the installation and monthly costs, which vary by state.
• Keeping calibration appointments. Each state sets how often the device must be calibrated and its data downloaded, so check the schedule in your court order or state program rules.

At each calibration visit, a technician will:

• Test the device for accuracy and adjust accordingly
• Download the data log
• Send the log to the authority monitoring your case, which reviews it for warnings and violations

The log records test results, engine starts and stops, disconnections, location and any sign of tampering, and all of it reaches the monitoring authority through that report.

Using an Ignition Interlock Device

Here’s how an interlock works on a normal drive. The device has two main parts:

• The handset. The piece you blow into, which measures your blood alcohol concentration.
• The relay module. The box under the dashboard that receives the result. If the sample passes, it sends a signal to the immobilizer that lets the engine start.

You’ll give breath samples at two different times.

Starting the vehicle. You’ll have to give an initial breath sample to start the car. The device analyzes the sample and compares it with the limit your state programs into it, called the set point. Most states set it at a lower level than the .08 BAC limit for driving, so a sample under .08 can still fail. If alcohol is detected above the set point, the car won’t start and the device waits a set time before it accepts another sample. Repeated failed tests are logged and can lead to a lockout, which the provider may need to clear. The lockout guide covers what to do if it happens.

Failed tests and other violations are logged and reported. Depending on your state and program, violation consequences can include:

• More time with the interlock
• Suspension of a restricted license
• Additional fees or fines
• Other penalties from the court handling your case

Rolling retests. Interlocks ask for more breath samples at random times after the engine starts, called rolling retests. This countermeasure is intended to prevent drivers from cheating the device by having a sober person give the breath sample.

While driving, the device will alert the motorist that it’s time for a rolling retest. Pull over somewhere safe if you need to, then give the sample within the time your device allows. A missed or failed retest is logged as a violation, and what happens next depends on your state’s rules.

How to Get a Court-Ordered Car Breathalyzer Installed

To get a court-ordered car breathalyzer installed, request a quote, schedule a time at a nearby service center and bring your paperwork to the appointment. Ignition interlock cost differs from state to state, so the quote depends on where your case is.

Have this information ready when you call or fill out the quote form:

• First and last name
• Home address
• State and ZIP code
• Contact information
• Driver’s license number
• Vehicle registration information including VIN and license plate
• Your court or DMV paperwork, including the case number, the court’s address, the presiding judge and your attorney
• County

Low Cost Interlock’s prices come with no hidden fees, flexible billing options and reporting included at no additional cost, and a Price Match Guarantee means it will beat another provider’s quote. You can get a quote in 60 seconds.

Your state determines which device you get. Depending on where you live, that’s the Co-Pilot, which has a Straight Blow feature and a numeric keypad, or the 777, which can take the Interlock Can cover. Devices are cleaned between clients, and how we keep our devices clean explains the process. To find a service center near you, check the interlock locations page.

Car Breathalyzer FAQs

Can I put a breathalyzer in my own car?

Yes, people can buy a voluntary in-car breathalyzer or a handheld tester for personal use. Those devices aren’t certified interlocks, so they don’t satisfy a court or DMV requirement and don’t count toward one later. If a court or your DMV requires an interlock, a state-approved provider has to install it. Low Cost Interlock schedules installs for drivers with a court or DMV requirement.

How accurate are car breathalyzers?

Certified interlocks are tested for precision and accuracy, and each state sets its own certification rules and the reading that counts as a fail. Some everyday products, including mouthwash and certain foods, can leave alcohol in your mouth and cause a false reading on a test taken right after. If a result doesn’t make sense to you, call support before doing anything else.

Will all cars have breathalyzers in 2026?

No. Federal law directed NHTSA to write a safety standard requiring new passenger vehicles to carry advanced impaired-driving prevention technology, and the agency opened that rulemaking with an advance notice in January 2024. An advance notice starts the process and doesn’t put a device in any car. For now, the breathalyzers in cars are interlocks installed for a court or DMV requirement and devices people choose to buy.

How much does a car breathalyzer machine cost?

For a court-ordered interlock, you lease the device instead of buying it, and the cost includes installation, a monthly lease with monitoring, calibration visits and removal. Each of those varies by state and provider. Low Cost Interlock’s pricing page shows what goes into a quote, and its Price Match Guarantee applies to competing quotes. Handheld and voluntary devices are sold at retail, and their prices vary by model.

Do they still put breathalyzers in cars?

Yes. Courts and state DMVs continue to require ignition interlocks after alcohol-related driving offenses, and the rules for who needs one differ by state. Cars don’t come with a breathalyzer as a standard feature, so a car breathalyzer is something added after purchase, either for a requirement or by choice.

Next Steps if You Need a Car Breathalyzer

Car breathalyzer and ignition interlock device are two names for the same equipment, and a certified one installed for a court or DMV requirement is the only kind that counts toward it. When a court or DMV requires an interlock, Low Cost Interlock can schedule the install at a certified service center near you. Schedule your installation, call (844) 387-0326, or reach out today with questions about your state’s requirements. If something goes wrong with a device that’s already installed, use the emergency tech support page.

Disclaimer: This article is provided by Low Cost Interlock for general informational purposes only and is not legal, financial, or medical advice. DUI and ignition interlock laws, penalties, fees, and program requirements vary by state, county, and individual circumstances, and they change over time. Any costs, timelines, or figures mentioned are general estimates, not quotes or guarantees. Nothing here should be relied on as a statement of the law in your jurisdiction. Always confirm current requirements with your state DMV, the court handling your case, a licensed attorney, or Low Cost Interlock directly before making decisions. Product features, pricing, availability, and promotions referenced are subject to change and may not be available in every state Low Cost Interlock serves.