An active disabling device stops a vehicle from starting or running if the driver has not met a condition — usually passing a breath test for alcohol.
The most common type is an ignition interlock device, which connects to your vehicle's ignition system. Before the engine will turn over, you blow into a tube attached to the device. If the device detects alcohol above a set threshold — typically 0.02% blood alcohol content — the engine will not start. Some devices also require you to blow again while driving, at random intervals, to make sure you have not been drinking since you started the car.
Active disabling devices are court-ordered in most cases. If you have been convicted of driving under the influence, a judge may require you to install one as a condition of keeping your license or as part of probation. Some states make them mandatory for a first offense; others require them only for repeat offenses or high blood alcohol readings. A few states allow you to choose an interlock instead of a license suspension.
The device itself is installed by a certified technician at an approved service center. Installation usually takes 30 minutes to an hour. You pay for the device, installation, and monthly monitoring — costs vary by state and provider, but typically range from several hundred dollars upfront to $60 to $100 per month. You are responsible for calibration checks, usually monthly, and for removing the device when the court order ends.
Key Takeaways
- An ignition interlock device requires a breath test before your vehicle will start, and is the most common type of active disabling device.
- Courts order these devices as part of a DUI conviction, and the specific rules depend on your state, your offense history, and the judge's decision.
- You pay for installation, the device itself, and monthly monitoring and calibration checks while it is installed.
- The device must be installed by a certified technician at an approved service center, and removed only when the court order expires or a judge lifts it.
How the breath test works
When you get in your vehicle, you insert the tube into your mouth and blow steadily for several seconds. The device measures the alcohol content in your breath and compares it to the threshold set by the court — usually 0.02%. If you are below that level, the engine starts normally. If you are at or above it, the ignition locks and the engine will not turn over.
Some devices also require a rolling retest — a second breath sample while you are driving. This happens at random times and intervals set by the device. If you fail a rolling retest, the device logs the failure and may trigger a horn or lights to alert you, but it will not shut off the engine while you are moving (doing so would be unsafe). However, the failure is recorded and reported to the monitoring agency, which may notify the court or your probation officer.
If you refuse to blow, or if the device cannot get a valid sample, it treats that the same way it treats a failed test — it logs the event and reports it. Repeated refusals or failures can result in the device locking your vehicle permanently until a technician resets it, or can lead to additional penalties from the court.
Who installs and monitors the device
Installation must be done by a technician certified by the device manufacturer and approved by your state's Department of Motor Vehicles or equivalent agency. You cannot install it yourself, and using an uncertified installer will not satisfy the court order. The technician will connect the device to your vehicle's ignition system, test it, and give you instructions on how to use it.
After installation, the device sends data to a monitoring agency — usually the company that made the device, or a third-party vendor hired by the state. This agency receives reports of every test you take, whether you passed or failed, and any refusals or technical problems. The monitoring agency sends these reports to the court, your probation officer, or both, depending on the terms of your sentence.
You are responsible for scheduling and paying for monthly calibration checks. These checks make sure the device is reading breath samples accurately. If you miss a calibration appointment, the device may lock your vehicle, and you may face additional penalties.
Costs and how long you wear one
The total cost of an ignition interlock device includes the device itself, installation, monthly monitoring, and calibration checks. Installation typically costs $100 to $300. Monthly fees range from $60 to $100, depending on your state and the service provider. Calibration checks are usually $10 to $20 each and happen once a month.
How long you must use the device depends on the court order. For a first DUI offense, many states require 6 months to 1 year. For repeat offenses, the requirement may be 2 to 3 years or longer. Some states allow you to petition the court to remove the device early if you have a clean record during the monitoring period, but this is not may provide.
The device stays in your vehicle until the court order expires or a judge orders it removed. You cannot remove it yourself — only a certified technician can do that. When the order ends, you schedule a removal appointment, the technician disconnects it, and you pay a removal fee (usually $50 to $150).
What happens if you fail a test or tamper with the device
A failed breath test is reported to the monitoring agency and forwarded to the court or probation officer. One or two failures may result in a warning. Multiple failures can lead to additional penalties: an extended monitoring period, a fine, jail time, or license suspension. The exact consequences depend on your state and the terms of your probation.
Tampering with the device — trying to disable it, remove it, or have someone else blow into it for you — is a separate crime in most states. It can result in criminal charges, jail time, and a longer monitoring period. The device is designed to detect tampering: it logs attempts to disconnect it, records if the tube is removed, and flags samples that do not match a human breath pattern.
If the device malfunctions or you believe it is reading incorrectly, contact the monitoring agency or the certified technician. Do not try to fix it yourself. A malfunction is different from a failed test, and the agency can investigate and adjust the record if the device was faulty.
Driving with an interlock device
Day-to-day, using an interlock device means blowing into the tube before you start your car every time you drive. This takes 30 seconds to a minute. You cannot start the car until you pass the test. If you have alcohol in your system — even a small amount — the device will not let the engine turn over.
If the device requires a rolling retest while you are driving, you will see a prompt on the device display or hear a tone. You then have a set amount of time (usually 5 to 10 minutes) to pull over safely and provide a sample. If you do not provide a sample in time, or if you fail, the device logs it as a violation.
The device does not prevent you from driving; it only prevents you from starting the car if you have been drinking. Once the engine is running and you have passed the initial test, you can drive normally. The device does not affect how the car handles or performs.
Removing the device early or transferring it to another vehicle
In some states, you can petition the court to remove the device before the order expires if you have maintained a clean record — no failed tests, no missed calibrations, no violations. The court may grant this request or deny it, depending on the judge and the circumstances of your case. There is no may provide of early removal.
If you need to drive a different vehicle during the monitoring period, you cannot straightforward move the device to the new car. You must contact the monitoring agency and request a transfer. A certified technician will remove the device from the old vehicle and install it in the new one. You pay a transfer fee, usually $100 to $200, in addition to the installation cost.
Some people own multiple vehicles and want to install the device in only one of them. This is allowed, but you can only drive the vehicle with the device installed while under a court order. Driving any other vehicle you own is a violation of the order and can result in additional penalties.
Frequently Asked Questions
Can I get the device removed if I move to another state?
No. The device must stay installed for the duration of the court order, even if you move. You will need to continue monthly calibrations and monitoring in your new state. If you move without notifying the monitoring agency, you may be in violation of the order. Contact the agency and the court before you relocate to understand the requirements in your new state.
What if I cannot afford the monthly fees?
Some states offer reduced fees or payment plans for people with low income. Contact the monitoring agency or your probation officer to ask about financial hardship options. In rare cases, a judge may reduce the monitoring period or waive fees, but you must request this formally through the court.
Does the device work if I have a medical condition that affects my breath?
Certain medical conditions — like diabetes, acid reflux, or respiratory infections — can affect breath alcohol readings. If you believe a medical condition is causing false readings, tell the monitoring agency and your doctor. The agency can adjust the device settings or investigate whether readings are accurate. Keep medical records and documentation to support your claim.
Can someone else blow into the device for me?
No. Having someone else provide a breath sample is tampering with the device and is a crime. The device is designed to detect this — it measures breath patterns and body temperature to confirm the sample is from the person assigned to the device. If you are caught, you face criminal charges and an extended monitoring period.
What happens if I am arrested for DUI again while wearing the device?
A second DUI while wearing an interlock device is treated as a separate offense and typically results in harsher penalties than a first offense. You may face additional jail time, a longer license suspension, and an extended interlock monitoring period. The new charge does not automatically remove the existing device order.