Drivers are being urged to not rely on off-the-shelf breathalysers to detect alcohol.
The Drinkaware group says it's seen a 'sharp rise' in queries from the public over the products.
However, it's warning that the devices are not developed to the same standards as those used by gardaí.
CEO Sheena Horgan said off-the-shelf breathalysers represent a "new and unregulated" space.
She observed: "We would have serious concerns about the validity of the results.
"While a personal breathalyser can be useful for information purposes, the results should not be taken as a clear indication that you are under the limit."
She added: "There is still a potential chance that you will be over the limit if stopped at an official gardaí checkpoint."
Changes to drink driving limits came into effect late last year.
Under the new rules, any drivers found with a blood alcohol concentration level of between 50mg and 80mg will receive an automatic three month driving ban and a €200 fine.
Drivers are also being advised to be cautious when driving the day after drinking, as there could still be alcohol in their system depending on the time of their last drink.