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Is A Blow Device Necessary To Drive After A DWI?

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As a DWI attorney in St. Louis, I am often asked whether or not a blow device will have to be put in your car. An ignition interlock is a device you blow into, and whether or not you will be required to have one depends on a few things:

Ignition Interlock Is Required When:

  1. Blow devices can be required by the Court as a condition of probation for anyone who is on probation for a DWI.
    • This is up to the Judge
    • This includes first-time offenses if the Judge orders ignition interlock as a ‘special condition of probation’
  2. Blow devices are required by law for 2nd and subsequent DWI’s
    • This isn’t up to the Judge, it is the law in Missouri
    • An ignition interlock is required for a minimum of 6 months from the time of reinstatement of the driver’s license.
  3. Blow devices are required by law if you are on a limited driving privilege (hardship license) during a long-term, alcohol-related revocation.
    • If you are revoked for “refusing to blow
    • If you are on a 5-year or 10-year denial
      • 5-year denial happens if you get 2 alcohol convictions within a 5-year period, or are convicted of DWI manslaughter.
      • 10-year denial happens if you have three or more convictions for DWI or DWI-related offenses

What About My Company Car?

There is an exception to the ignition interlock requirement, but only if you get a court order that allows you to drive your employer-owned vehicle without an ignition interlock device.

  • You can drive without interlock for employment-purposes, in an employer-owned vehicle only
  • This does not apply for self-employed people or owners of businesses that have employer-owned vehicles.

What Happens If I Get Caught Driving Without A Blow Device?

If you are required to have Ignition Interlock and you are caught driving without a blow device:

  • This is a Class A Misdemeanor in Missouri
    • Carries a penalty of up to 1-year in county jail and a maximum fine of $1,000.00.
  • Your License will be revoked if you plead guilty:
    • 1 year for a first offense
    • 5 years for second and subsequent offenses

Author Bio


Matt Jett is the CEO and Managing Partner of Jett Legal, a Missouri personal injury law firm. With more than 10 years of
experience in personal injury, he has zealously represented clients in various legal matters, including car and truck
accidents, workers’ compensation, wrongful death, and other cases.

Matt received his Juris Doctor from the University of Missouri-Columbia School of Law and is a member of the Missouri
Bar Association. He has received numerous accolades for his work, including the Rising Stars distinction by Super Lawyers 2019-2022.

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