What Is a Car Breathalyzer Called? | Official Names Explained

The device commonly called a car breathalyzer is officially known as an ignition interlock device (IID).

If you’ve searched what is a car breathalyzer called, you’ve probably seen a mix of terms and wondered if they all mean the same thing. The short answer is yes — but the formal name matters if you’re dealing with courts, DMVs, or insurance requirements. This guide breaks down the official terminology, how the device actually works, and what it does and doesn’t do.

What Is the Official Name for a Car Breathalyzer?

The formal term used by government agencies and DUI programs is ignition interlock device, or IID. The National Highway Traffic Safety Administration (NHTSA) defines an alcohol ignition interlock as a breath-test device connected to a vehicle’s ignition system.

Depending on the state or program, you may also see it called a breath alcohol ignition interlock device (BAIID) — Wisconsin’s DOT uses this term — or simply a breathalyzer in everyday conversation. The common name “car breathalyzer” is widely understood, but official materials almost always use “ignition interlock device.”

In short:

• Ignition interlock device (IID) — the standard formal term
• BAIID — an alternative official acronym used by some states like Wisconsin
• Car breathalyzer — common everyday language for the same device

How an Ignition Interlock Device Works

The device is wired directly into the ignition system. Before the engine starts, the driver must blow into a handheld mouthpiece. The system measures breath alcohol concentration (BrAC) and either allows the starter relay to engage or blocks it entirely.

NHTSA notes that interlocks typically use a preset threshold of 0.02 BrAC — far lower than the legal driving limit of 0.08. If the sample exceeds that level, the vehicle simply won’t start.

Most modern systems also require rolling retests while you’re driving. At random intervals, the device prompts another breath sample to make sure the driver hasn’t switched with someone else or started drinking after the initial test. NHTSA says a data recorder logs every test result, which is how monitoring agencies track compliance.

Do Police Breathalyzers and Car Interlocks Differ?

Yes — and confusing the two is a common mistake. A field police breath test is a portable device an officer uses at a traffic stop to estimate your BAC. That’s not a car breathalyzer. The term “car breathalyzer” refers specifically to the permanently installed ignition interlock that’s part of a vehicle’s electrical system.

The purposes are completely different:

• The police unit is a one-time evidentiary test taken after a stop
• The interlock is a continuous prevention measure installed in your car
• Police breathalyzers are portable; interlocks are hardwired into the ignition

Who Needs an Ignition Interlock Device?

Ignition interlocks are typically ordered by a court or a state’s motor vehicle division as a condition of probation or license reinstatement after a DUI or DWI conviction. They’re part of a structured program, not a consumer product you buy off a shelf.

That statistic is why most states now require them for at least some offenses, and why programs are expanding to first-time offenders.

You can’t just buy one and install it yourself for legal compliance. These devices are typically leased through approved interlock providers, professionally installed, and monitored for the duration of the court order. Installation depends on your vehicle’s ignition and electrical system, and a self-installed unit won’t satisfy program requirements.

State rules vary considerably. Wisconsin’s DOT, for example, uses the term BAIID and spells out its own requirements. Some states mandate IIDs for all DUI convictions; others reserve them for high-BAC cases or repeat offenders. Retest intervals, monitoring periods, and legal consequences all differ by jurisdiction and court order.

If you’re exploring options for monitoring alcohol use in a vehicle, it’s worth understanding the distinction between court-ordered interlocks and personal breathalyzer devices. For a closer look at consumer-level car breathalyzer options, see our tested roundup of the best car breathalyzer devices.