Hound Labs, a startup that aims to make the first marijuana breathalyzer, raised a fresh $30 million on Tuesday.

The California-based company also published the first study offering a glimpse at how the handheld device works. It contains some important limitations.

Today, there's no good way to determine if someone is too high to work or drive.

Hound Labs has now raised a total of $65 million. Notable investors include Dick Wolf, the creator of 'Law & Order.'

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A startup aiming to make the first marijuana breathalyzer raised a fresh $30 million on Tuesday and also published the first study offering a glimpse at how the device works.

If successful, the technology could help employers and police distinguish between people who've used cannabis legally — in the past — from people who are currently impaired, either while driving or on the job. As more states legalize marijuana, investors are betting that demand for such a device could be substantial.

Oakland, California-based Hound Labs told Business Insider it aims to start rolling out the device this winter. The tool also measures alcohol like a standard breathalyzer.

Mike Lynn and his wife, Jenny, founded Hound Labs in 2014 at the peak of marijuana legalization efforts across a half-dozen states. That year, voters in three states including Oregon approved measures to legalize recreational cannabis; voters in two more states including New York chose to legalize medical marijuana.

Mike is a reserve deputy sheriff, current emergency room physician, and venture capitalist. Jenny previously served as head of marketing for two large advisory firms.

A unique device that would fill a big need

The Lynns' technology would be the first of its kind.

Today, there's no reliable legal way to tell if someone is too high to work or drive. Instead, police use rough "field sobriety" tests like standing on one leg, for example, or urine or saliva tests, which can only tell if someone's used in the past few days — not whether they're impaired at the moment.

But making a marijuana breathalyzer isn't as straightforward as making one for alcohol. When someone who's been drinking exhales, it's fairly easy to pick up on relatively high levels of booze on their breath. When someone who's been vaping or smoking exhales, cannabis is detectable only in minute amounts — making it difficult to pick up.

Mike Lynn likened it to "finding the needle in 10,000 haystacks," he previously told Business Insider.

Read more: This ER doctor is about to debut the first marijuana breathalyzer, and he's already raised $35 million from investors including the creator of 'Law & Order'

A small study with some important limitations

So in its new study, Hound aimed to show that its handheld device could reliably spot the fine traces of marijuana exhaled by a group of 20 volunteers who smoked, vaped, and used edibles. Using Hound's tool (which users blow into for a minute) and a standard blood test, researchers at the University of California, San Francisco tested the volunteers every 15 minutes for the first hour they'd consumed and then every 30 minutes until 3 hours had passed.

The findings were published last month in the journal Clinical Chemistry.

Read more: Here's how long various drugs stay in your body

The study was small and paid for by Hound, but it suggested that the device could detect recent marijuana use.

It also had some limitations, however: Researchers didn't compare people who'd smoked against people who did not, for example, and the results varied pretty dramatically among the participants, which could mean it's still too early to come up with an objective numerical figure for "impaired" cannabis use.

Still, investors are hopeful. Many of them say that as marijuana legalization efforts spread, we need better ways of differentiating between people who are currently impaired from those who've consumed cannabis legally in the past.

Other researchers have previously explored the idea of a marijuana breathalyzer. And there's a Canadian startup that's also aiming to make a handheld device. Called SannTek, they recently debuted at a demo day led by Y Combinator, the famous accelerator founded by Silicon Valley icon Paul Graham.

Earlier this year, Hound got funding from Dick Wolf, the creator and executive producer of the hit television series "Law & Order." On Tuesday, VC firm Intrinsic Capital Partners led the fresh $30 million round, joined by NFP Ventures, the investment arm of one of the largest US insurance brokers, and Main Street Advisors. Existing backers Icon Ventures and Benchmark Capital also contributed to the latest raise.

Hound's device could replace hair and urine testing

Hound said it has now raised a total of $65 million. The company declined to provide its valuation.

Shawn Ellis, a managing director at NFP Ventures, sees Hound's device as a potential solution to poor hair- and urine-based drug testing methods currently used across industries like construction and trucking. Those tests can't distinguish between someone who just smoked and someone who used several days before.

"It's a huge leap forward to move away from hair and urine testing," Ellis told Business Insider.