Does a Car Breathalyzer Detect Marijuana?

With cannabis products now legal for recreational and/or medical use in some states, it’s important to remember that driving while high remains illegal (and dangerous) everywhere. That’s why law enforcement agencies across America are working hard to keep people under the influence of cannabis off the road.

For decades, Ignition Interlock Devices like Smart Start’s have been some of the most important tools for Separating Drinking From Driving®. Thus, as cannabis legalization continues to spread, you might be wondering if there are “marijuana breathalyzers” for vehicles or Ignition Interlock Devices that can detect weed. Right now, the answer is no — but read on to learn about how law enforcement is developing new tools to help in the fight against drugged driving.

Does a Breathalyzer Detect Weed In an Ignition Interlock Device?

No, the Ignition Interlock Devices (IIDs) that many drivers are required to install on their vehicles after getting a DUI do not detect marijuana use. Currently, no IID technology is available that can detect marijuana on a driver’s breath.

So why can’t a car breathalyzer detect weed? The fuel-cell technology that breathalyzers use was developed specifically to detect alcohol. Some of the properties of alcohol make it especially easy to detect on a person’s breath, but that’s not the case with THC (the chemical in marijuana that creates the “high” sensation). 

That doesn’t mean that it’s safe or wise to use cannabis products while driving or before driving. In fact, it’s very dangerous: Cannabis slows your reaction time, impairs your judgment, and has other negative effects on your driving abilities. Impaired driving is always dangerous, whether a driver is impaired by THC, alcohol, or another substance. 

Why It’s Hard to Detect Marijuana Impairment

With many current tests for marijuana, it can be hard to distinguish whether a person has recently consumed marijuana. That’s because the THC metabolites that the tests detect are stored in fat cells, so they can continue to show up in people who used cannabis products days or even weeks ago, according to WebMD.

Researchers have been working hard on a solution to this problem, and several states have rolled out pilot programs to test new drug-detection technologies. In Indiana, for example, some police departments have begun equipping officers with an improved oral fluid test that identifies recent marijuana use, along with other drugs like cocaine and methamphetamine. So, while there are still challenges in reliably detecting marijuana usage, new technologies are pushing the field forward.

Can You Get a DUI for Driving High?

Yes. Many states have laws that criminalize driving a vehicle while under the influence of marijuana or any other drug. Different states use different definitions of driving while under the influence of marijuana, including:

• Zero-tolerance: Any amount of THC in your body
• Per Se: An amount of THC in your body over a predetermined limit
• Under the Influence DUID: Any amount of THC that impairs your ability to drive

While it can be more challenging to prove that a driver is impaired by marijuana, that’s no protection against all of the challenges that a DUI can bring into your life. You could face probation, fines, jail time, a suspended driver’s license, and other potential consequences that come with a DUI. You can help keep our roads safe by finding another way home, even if you think you’re able to drive. Assign a designated sober driver or take advantage of other options like taxis, rideshares, or public transit. 

Frequently Asked Questions About Car Breathalyzers and Marijuana

• Can a standard breathalyzer in an Ignition Interlock Device be modified to detect marijuana?

  • No. Only tests specifically designed to identify THC can detect its presence. 

• Are marijuana breathalyzers available for use in Ignition Interlock Devices (IIDs)?

  • So far, no state has approved any breath sample-based method for detecting cannabis use via an Ignition Interlock Device.

• Does marijuana show up on a DUI blood test?

  • It could, depending on what the blood sample is tested for. If you receive a blood test as part of a DUI arrest, the sample might be tested only to establish your blood alcohol concentration (BAC), but it might also be tested for THC and other drugs. 

While Smart Start doesn’t offer marijuana breathalyzers, we’re always keeping up with the latest developments in Interlock Device technology. Learn more about how breathalyzers work, or get in touch with our Program Advisors to find the right Interlock Device for your DUI program.