Drivers using cheap do-it-yourself breathalysers to ascertain if they are fit to drive after drinking are leaving themselves open to prosecution after tests showed that the units are unreliable and often give false readings.

A range of devices, costing between £2.49 and £15.99 and advertised on the internet, were tested by Fleet News’ sister title Parker’s.

With the help of West Yorkshire Police and Medacx, a supplier of breathalysers to UK police forces, the systems were subject to scientific tests which involved the breathalysers being used after a driver had drunk enough alcohol to be over the legal drink-drive limit.

Every device tested gave a different alcohol reading to the official police unit, while more than half of the devices showed that it was safe for the person to drive despite being over the legal drink-drive limit of 35 micrograms of alcohol in 100 millilitres of breath.

The majority of the devices tested bore no manufacturer’s name and were imported from Hong Kong and China.
Inspector Russell Clark, of West Yorkshire Police, said: “Anyone who is stopped for drink-driving will, as a very minimum, lose their licence for six months.

If someone was to cause a death as a result of drink-driving, they’re looking at a possible 14-year prison sentence.

“Hand-held breathalysers are no defence if anyone should go to court.

"There is no safe level for drinking and driving, aside from not drinking at all.”

Breathalysers have to undergo rigorous tests before being granted type approval, which means they can be used by police forces.

None of the devices tested had type approval.

The tests have resulted in calls for more regulation in the market.

Hunter Abbott, managing director of Alcosense, which makes a respected self-test breathalyser which is triple-checked for accuracy and which was not a part of the test, said: “We desperately need to see regulation of breathalysers in the UK.

“At the moment there’s a free-for-all and there’s no test for accuracy or consistency, which means anyone can sell a device and it doesn’t have to be accurate.”