You have probably noticed that there are various tools to help measure blood alcohol concentration:
Many factors influence the results of a blood alcohol concentration test, including the device’s reliability, maintenance, calibration, misuse when used while drinking alcohol, the fact that the absorption and elimination of alcohol varies from one individual to the next, and the fact that blood alcohol concentration can keep increasing up to one hour after the last drink.
With regards to impaired driving, scientific literature amply shows that the increased risk of having an accident is significantly high, well before blood alcohol concentration reaches 80 mg of alcohol per 100 ml of blood.
In other words, it is best to avoid using these tools and devices to prevent impaired driving. Instead, plan on using alternative solutions such as taking a taxi or using a rideshare service, taking public transit, using a drive-home service, having a designated driver or sleeping over.
For more information: What the Law Says, Myths and Facts About Drinking and Driving, Responsibilities and Smart Solutions (SAAQ) and Évaluation de 10 modèles d’alcootest (Protégez-vous, in French only)