Now that marijuana use is legal in many states, employers need a way to distinguish very recent use from past use.

“’We don’t want to know what you did a week ago, or two weeks ago, because it doesn’t impact your impairment today,’ said Warren Tolman, director of business development for Hound Labs.”

“The thing that’s groundbreaking about this test is it can distinguish recent use from historic use,” Mr. Boxer said. “An employee in many states has a legal right to use cannabis.”

“It’s a game changer,” said John Hudak, a senior fellow at the Brookings Institution who has written extensively on marijuana legalization.

“I actually do see it as benefiting all parties,” he told the Bee. Most tests currently used by employers reveal marijuana use stretching back as far as 30 days, meaning workers could be penalized in some cases even if they are not high on the job.

As more states legalize recreational marijuana, law enforcement is hoping to detect those driving under the influence. NBC News received an exclusive look at a new breathalyzer, tested by officials on the streets over Labor Day weekend. NBC’s Stephanie Gosk reports for TODAY.

The device would be able to test if someone had smoked within the past three hours. Some locals […] say that marijuana breathalyzers could crack down on impaired driving and it could be beneficial to businesses.

Developing the breath test has been “amazingly challenging science,” but building a device to do it has grown exponentially more important as more and more jurisdictions legalize both medical and recreational marijuana use, Lynn said.

Lynn said he expects the Hound Labs device will also be used in the workplace, where employers can ensure that workers are not high on the job, and employees won’t face sanctions if they partied the day before.

Old tests for marijuana looked for trace elements in things like blood, urine, and hair. But legalization changed all of this. Suddenly marijuana testing became a spectrum, with the need to delineate between the person who threw five on it a week ago, but who still has evidence of weed in their bodily fluids, and the person who’s dangerously blazed right this moment.