Pocket breathalyzers are not always accurate and could give drivers a false sense that they're sober enough to get behind the wheel, say traffic safety groups.

The devices, sold for about $10 under names such as the Alcohol Tester, are available at stores across Canada such as the Bay, Wal-Mart and Zellers.

They operate much the way a roadside alcohol test does: a driver blows into the mouthpiece and if their blood alcohol level is above the legal limit of .08 per cent, a red light is ignited.

Andrew Murie, the CEO of MADD (Mothers Against Drunk Driving), says his group does not endorse the devices because they often give inaccurate readings.

"Basically, the reliability of the equipment for false negatives is really high," he told Canada AM Tuesday. "And so it's like playing Russian roulette with your safety and others on the roadway."

Murie says his biggest worry about the devices is that drivers will get inaccurate results from them and will continue to drink beyond the legal limit.

"Then you get behind the car and you cause carnage out there that is unnecessary. So the public shouldn't rely on this really cheap type of -- it's really a gizmo," he says. 

The price of the tiny devices alone should raise eyebrows, Murie says, since the equipment that police officers use cost thousands of dollars, require extensive training to use and have to be tested and recalibrated regularly.

Murie says he's not just disappointed in the device's accuracy; he says that drivers shouldn't be using them at all.

"It sends the wrong message. You should never drink up to the legal limit," he says. "If you're going to drink, separate it from the driving."

But the Bay says the pocket breathalyzer has been very popular and has become a hot seller.

"Given the popularity of the product, consumers are clearly demonstrating they're engaging with the worthwhile message MADD is spreading about responsible drinking," says corporate communications director Hillary Stauth.

One of the manufacturers of the devices, Resource Management International, has also defended its Connectables Breathalyzer tester.

"We do not condone drinking and driving," the company said in a recent statement. "The Connectables Breathalyzer allows consumers access to a reliable and affordable alcohol-testing device that can take the guesswork about whether it is safe to drive. It is designed to create awareness and responsibility."

Curie adds that he believes that the legal limit in this country is far too high. That's why MADD is now lobbying the government to lower the legal blood-alcohol limit to .05 per cent, though he concedes that their efforts have stalled now that the country is into a federal election.

"But we still believe and the public should believe that the guideline of .05 and lower is where you should be. Because intoxication starts at the first drink and as low as .03."