Drivers are being warned that they could be caught out if they trust cheap personal breathalysers currently on sale.

Some service stations are selling electronic breathalysers for as little as £4.99 to take advantage of the Christmas season, but experts are telling drivers not to rely on the equipment.

It takes one hour to absorb one unit, and another hour (although this can vary by up to 20% either way depending on the individual) for each unit to exit the body.

Many of the devices come with disclaimers warning that they should only be used as a guide, but the concern is drivers will miss the small print and use them as a definitive indication of whether they are fit to drive.

It may say you are OK but the police officer’s device will be the one your future is decided on, not the garage’s. Please do not forget even if it is accurate, your level could be rising as you absorb the alcohol, leaving you “over” by the time you drive.

So unless you abstain, the only reliable way to assess whether you are over the drink-drive limit is to add up the number of units, and count them down until you are alcohol free and therefore safe to drive.

It takes one hour to absorb one unit, and another hour (although this can vary by up to 20% either way depending on the individual) for each unit to exit the body.

It’s all to complicated so simply don’t drink if driving

FemaleFirst Jackie Violet