BOULDER, Colo. The Boulder laboratory for the National Institute of Standards and Technology (NIST) is working to determine if its possible to make a breathalyzer that detects the tetrahydrocannabinol (THC) present in cannabis, instead of detecting the ethanol present in alcohol.With the alcohol breathalyzer, we're detecting the ethanol molecule, said Kavita Jeerage, a materials research engineer for NIST. It is a simple model. We know a lot about its properties. It's obviously a liquid, but it's also very easily carried in breath as a vapor molecule, a gas molecule.Detecting THC molecules is far more complicated.Tetrahydrocannabinol, which is the primary psychoactive molecule in cannabis, is a very large molecule, said Jeerage. It's a complicated molecule, and it has not received as much study, and that's partly because its a very difficult molecule to study. Its properties are challenging to measure. Scientists at NIST have been eyeing a way to analyze a persons breath and determine levels of THC since Washington and Colorado first legalized marijuana. They foresaw that companies would want to develop breathalyzer-type devices, and realized that companies would need as much information as possible about THC in breath to make sure that those devices worked as intended.Would Colorado and Washington stay as outliers, or would legalization spread throughout the country? said Jeerage. Essentially, as more states loosened their regulations, it became more of a national problem. Eventually our effort grew, as well.NIST partnered with University of Colorado Boulder and UCHealth Ancshutz to get participants for their studies. NIST does not provide any participants with cannabis. They purchase their own cannabis and then participate in the studies in mobile vans, in CU Boulders case, or in special off-campus rooms at UCHealth Anschutz.The goal of these studies is not to create a breathalyzer that detects THC. Its to provide accurate, public data so that companies can develop their own tools. There are a lot of questions still left to answer.Did someone recently use cannabis? Can we tell that they recently used cannabis? said Jeerage. Then there's the question of, what that window is, can we detect cannabis use an hour after cannabis was smoked, two hours after it was smoked? We're trying to get that information.