The standard US term for a car breathalyzer is an ignition interlock device (IID).
If you’ve heard “car breathalyzer,” “blow and go,” or “BAIID,” they all point to the same thing: a device installed in a vehicle that requires a breath sample before the engine will start. Knowing the correct name matters because it’s the term you’ll need when researching state requirements, talking to your probation officer, or shopping for an approved device.
The official name used by the National Highway Traffic Safety Administration (NHTSA) and nearly every state DMV is ignition interlock device, commonly shortened to IID. Some states and regions use variations like “alcohol ignition interlock” or “alcolock,” but IID is the universal, recognized term.
What an Ignition Interlock Device Does
An ignition interlock device is an aftermarket unit connected directly to your vehicle’s ignition or starter system. It functions as a breath alcohol sensor that tests your breath before you can start the car. If the detected alcohol level is below the preset limit, the vehicle starts normally. If not, it stays locked.
The device includes three core components:
- A breath alcohol sensor (typically a fuel-cell device)
- A control unit connected to the ignition
- A data collection system that records test results
Many modern units add features like cameras and GPS, which some states require to verify the person blowing is actually the driver.
Rolling Retests: Blowing While Driving
Beyond the initial start-up test, many IID programs require rolling retests. At random intervals while you’re driving, the device prompts you to blow again. Pennsylvania’s DMV notes drivers are prompted at periodic times to provide another sample while the vehicle is in operation.
This feature exists to stop a driver from having someone else blow to start the car, then drinking while driving.
The table below summarizes the main things to know about how these devices work:
| Function | What Happens | Why It Matters |
|---|---|---|
| Start-up test | You blow into the mouthpiece before starting | Engine won’t start if alcohol exceeds the limit |
| Rolling retests | Random re-tests while driving | Prevents drinking after the car is running |
| Data recording | Unit logs every test result and attempt | Officials review logs at calibration visits |
| Fuel-cell sensor | Measures breath alcohol precisely | More accurate than consumer breathalyzers |
Different Names, Same Device: BAIID and Blow and Go
While IID is the official term, you’ll encounter several other names depending on where you live and who you’re talking to. Illinois uses BAIID (Breath Alcohol Ignition Interlock Device), and Michigan uses the same acronym in its program materials. “Blow and go” is the informal, often-used street term for the device.
Each state runs its own ignition interlock program, and the Vermont DMV explains that the device is installed in a vehicle and connected to the ignition system, requiring a breath sample before the vehicle will start. Because state programs differ, installation costs, calibration schedules, retest timing, and reporting requirements vary by jurisdiction.
If you’re preparing to get an IID installed, it’s worth checking which models your state approves. Your state’s list will tell you which certified providers you can use — you can’t simply buy any device off the shelf.
What an IID Costs and Who Needs One
Ignition interlocks are most commonly required for drivers convicted of DUI or DWI, often as a condition of probation or license reinstatement. The specific rules depend on your state and the severity of the offense. Some states require them for first offenses; others only for repeat offenders or high-BAC cases.
Pricing varies widely by state, provider, and the length of your required installation period. Because costs are set by individual vendors and state programs, the best approach is to contact approved installers in your area for a quote. Most programs require monthly calibration visits, and those service fees are typically the larger ongoing expense. If you’re looking to understand your options and compare providers, our roundup of the best car breathalyzers breaks down the top-rated models on the market.
References & Sources
- NHTSA. “Ignition Interlocks: What You Need to Know.” Defines IID, the.02 BAC limit, and device components.
- CDC. “Ignition Interlock Devices.” Explains how interlocks work and their role in preventing alcohol-impaired driving.
- Vermont DMV. “What is an ignition interlock device?” Provides the official definition of an IID and how it connects to the ignition system.