We tend to entertain a range of questions from people interested in interlock devices, and this is probably one of the more common. It’s a logical inquiry: Can an ignition interlock device detect drugs? While interlock devices are known to detect alcohol levels beyond .025, or whatever your state’s limit may be, they are unable to detect weed and other drugs in your system.

A Little Background Info

Blow N Go’s ignition interlock device (IID), or car breathalyzer, is a small gadget that attaches to your vehicle’s starter system and requires the measurement of the driver’s blood alcohol concentration (BAC) level prior to starting the vehicle. We use the newest ignition interlock machines to do this, touting the latest technology and a stamp of approval from the MVA. By blowing into the interlock both before and during the operation of your car or truck, and confirming your BAC is below the programmed level mandated by your state’s law, your vehicle will start as normal. If your BAC is above .025 (for Maryland), your vehicle will not start until you provide a breath sample that no longer detects alcohol above the legal limit.

So, Tell Me...

Inquiring minds do want to know – if an interlock can detect BAC levels, can it also detect drug levels? Due to ethanol-specific fuel-cell sensors, the answer is no. Our sensors require three things:

•   that a chemical oxidation reaction occurs, using

•   a catalytic electrode surface (typically platinum), and that

•   an electric current is produced.

  The most important part of this process is the catalyst. Using the clue of ethanol above, can you guess the answer? That’s right—it’s alcohol, which is the chemical the interlock is programmed to convert into an alcohol-equivalent reading. And while there is talk of the development of devices that would measure THC, also known as tetrahydrocannabinol, in a person’s system, Blow N Go currently only offers alcohol-specific fuel-cell interlock devices.

  A Note of Caution

  Be aware, that in Maryland, a personal is guilty of DUI while he or she is driving any vehicle so far impaired by any drug that the vehicle is operated unsafely or driving any vehicle while the driver is impaired by any controlled dangerous substance if the person is not entitled to use the substance under the law. So, while an interlock device cannot detect marijuana in your system, should you be pulled over, even after blowing clear (from alcohol) into your device, you may still qualify for a DUI.