"We've been selling them for about seven years and this has been the biggest boom we've had. We can hardly keep up with supply. It probably started about three weeks before December 1 [when the drink-drive limit was dropped from 400mg of breath-alcohol to 250mg]. And it hasn't stopped.
"A lot of workplaces are using [them] for after-work drinks and a lot of Christmas presents."
The Weekend Herald tested a man and a woman drinking 330ml bottles of 5 per cent alcohol beer, over a period of four hours. Following each beer, as per the requirements of the breathalysers to get accurate readings, there was a 20-minute stand-down period with no eating or drinking before being tested.
Three of the devices tested were electronic digital breath-alcohol readers, while the other was a $9 disposable unit with colour-change crystals.
Tester Forrester McKee, 22, said it was useful to determine how much he could drink and be safe to drive.
"It's really good to know and be informed about how many drinks you can have before you're over the limit. It would obviously be a good tool to have if you were out and you planned on driving."
The machines were all easy to use, he said.
Aleysha Kelly, 22, the other participant, agreed it was good to know that she could drink three beers before hitting the limit. "But I'm not going to push it. I'm only going to have two drinks when I go out. Then I definitely know I'm under [the limit]."
The only breathalyser she didn't like was the disposable one, which required the user to snap two ends of a vial containing crystals, tip out the excess crystals at each end, blow in a bag, then attach the vial to the bag and push the air out of the bag through the crystals in the vial.
Up to the red line, it indicates you are under the limit. Over the red line, it indicates you are over.
"The blow-in-the-bag one, although it's just an indicator, it's hard. If you were out at the pub you couldn't really test that one at the bar. It's not that appropriate."
A police spokesman said personal breathalysers were a guide only.
"Our message is that there is no 'safe' amount of alcohol to drink before driving. Alcohol affects everyone differently, so while personal breathalysers may provide a guide, they should not be relied upon.
"Police will certainly not accept any such method as an excuse if someone is caught exceeding breath or blood alcohol levels."
Gavin Foster, at Sober Check, said individuals, as well as businesses and some pubs, were buying up the testers.
While the top-shelf machine he sold - the Lifeloc FC10 - was "law enforcement" grade and good for businesses, cheaper ones were available for personal use.
The quality was dictated by how well the machines tested after 12 months' use, because some models would become less accurate over time, he said.
Others that were not tested, which sell for $5 to $20, should be avoided as they were essentially "random number generators", he said.
