Car breathalyzers

All about car breathalyzers 


An ignition interlock device, also known as a car breathalyzer or breath alcohol ignition interlock device (BAIID), is a mechanism that prevents a vehicle from starting if alcohol is detected on the driver’s breath. The device is comprised of a handheld unit, a removable mouthpiece and a relay cord that hooks into the vehicle’s ignition system. 

An ignition interlock system combines a breathalyzer with electronics to bypass the ignition in your car.  It is about the size of a normal handheld breathalyzer with a cable that disappears under the dash.  


You have to use the breathalyzer before you can start your car.  If you blow more than a 0.0 then your car will not start.  The typical interlock system has many safeguards to minimize cheating.

You must have a car breathalyzer or ignition interlock device installed if you are trying to obtain the following:

  • Reinstatement of your driving privilege
  • Issuance of a Limited Driving Privilege (LDP)
  • Issuance of a Restricted Driving Privilege (RDP) - Points (Alcohol)
  • Issuance of a Restricted Driving Privilege (RDP) - Alcohol


While you are operating the vehicle, the IID will alert you to submit a breath sample. This breath samples are random and are typically required several times while you are operating the vehicle. 

If the device detects that you have a breath alcohol level above the pre-set limit while you are driving, depending on your jurisdiction, the device will sound an alarm and may also trigger the vehicle’s horn and/or flash the lights until you turn off the vehicle. 

For safety reasons, the IID will not turn off the vehicle if your breath alcohol level is above the pre-set limit while you are operating the vehicle. Some devices also notify law enforcement if your breath alcohol level is above the pre-set limit while you are operating the vehicle.

Prior to starting the vehicle, the driver is required to submit a breath sample into the mouthpiece of the device using a specific pattern of blowing, inhaling and/or humming.

The actual method of providing the sample is determined by state regulations and each individual interlock provider. If the breath alcohol concentration (BrAC) is below the limit set by the state, the vehicle will start. If the BrAC is over the set limit, the vehicle will not start until a passing sample has been submitted.


During your blow test, there are 4 things that the IID requires in order to pass: 

  • Proper breath temperature 
  • Breath volume 
  • Breath pressure 
  • Vibration. The only ones you need to be cognizant of are breath volume and breathe pressure. When blowing into the device, it is important to ensure you are blowing a lot of air, as well as the right amount of pressure into the mouthpiece. 


You can conduct a regular blow, a blow-suck-blow, or blow-hum-blow technique when giving your sample. All will give a proper test for the IID with the right air volume and pressure.

During your driving period, you may be subject to rolling tests as well. The car breathalyzer will notify you as you drive when it is time to sample your breath while using your car. Be careful when doing this because we know some drivers prefer to pull over safely to give the breath sample while others can manage while driving. Use common sense when conducting the rolling retests.


Whether you drive and test or pull over to the side of the road to test, it’s important to know that your car will not shut down if you fail the breath test while driving. You will have an opportunity to safely pull over and park your car after a failed test. Again, please note that your vehicle will NOT shut down during a rolling retest.
The car breathalyzer itself is meant to be minimally intrusive as a device in your vehicle.


Today’s ignition interlock systems have more benefits to consumers; they are lightweight and about the size of a cell phone. The unit is located in the glove box of your vehicle and hardwired to the dashboard comfortably positioned where you can blow a sample of air in to the car breathalyzer when needed.

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