“Marijuana is legal, as is alcohol,’ said Hound Labs’ Mike Lynn. ‘But we’re not allowed to drink beer and drive, and there’s an absolute reason why people are not allowed to smoke pot and drive.”

“Having a marijuana breathalyzer that — for the first time — can focus on those people who have used pot in the last few hours, it transforms the ability in a fair way to determine who’s potentially impaired and who isn’t.”

“’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 difficulty with [blood testing] is police typically need a judge’s approval and then need a trained phlebotomist to draw the blood, a process that can easily take a couple of hours. By then, studies show, most of the THC in blood has already dissipated, even though the person may still be impaired.

“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.”

“A test like that would frankly make sense,” Armentano [deputy director of the National Organization for the Reform of Marijuana Laws] said. “Just like we wouldn’t allow employees to have a couple drinks and show up to work.”

“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.

FOX Business’ Susan Li breaks down a new report on marijuana breathalyzers that detects pot-use within three hours.