Researchers are building a THC breathalyzer - A breakthrough that could change how marijuana DUIs are detected
The need for a device that can rapidly detect if drivers are under the influence of marijuana has spurred research to find a solution. One may be on the way.
As states change laws related to marijuana usage, law enforcement agencies across the nation are in need of an easily deployable tool that will allow them to quickly detect if a driver is under the influence of the drug. This has led to researchers developing an inhaler-like device that can be used on the roadside and doesn’t require further laboratory analysis.
Emanuele Alves at Virginia Commonwealth University (VCU) published the results of the project he led earlier this year on the Office of Justice Programs’ National Criminal Justice Reference Service. He detailed that the THC breathalyzer prototype created was able to separately detect delta-9 THC and CBN independently from CBD, which was the main goal of the project. The former two are both psychoactive to some degree while the latter one isn’t.
How does the THC breathalyzer work?
The THC breathalyzer prototype looks similar to an inhaler that people with asthma use with a disk attached that would hold a cartridge. The person being tested blows into the device and their breath is collected on a chitosan film impregnated with Fast Blue dyes that change color when reacting with cannabinoids.
🌿 4/20 might not be an official holiday, but the government's got plenty to say about weed.
— USAFacts (@USAFacts) April 20, 2025
In fact, the DEA has a list of 300+ slang terms for marijuana. (Yes, our team counted.)
And cannabis laws are a total trip, with some states saying "puff puff pass" while others give a… pic.twitter.com/Zee2Rbe1Kq
The person analyzing the THC breathalyzer results can differentiate between the cannabinoids based on the color hue of the colorimetric response. These results are reliable from between 10 and 100 nanograms, but Alves cautions that further research “needs to be completed to determine at what concentration the cannabinoids can no longer be differentiated from one another.”
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