Fact: An often-cited decades-old study found that hyperventilation and vigorous exercise did indeed lower subjects’ BAC readings by as much as 10%. Conversely, holding their breath actually increased subjects’ BAC readings by up to 20%. Unfortunately, these activities can also render one light-headed and gasping for air – behaviour that would undoubtedly capture the attention of law enforcement officers who suspect an individual of being under the influence.

Fiction: Breathalyser test results can be used in court.

Fact: Breathalysers are used as preliminary roadside screening tools to help law enforcement officers assess drivers’ suspected of being drunk. Breath test results may help an officer determine if a subject should be arrested for suspicion of DUI, but results are not always admissible in court.

Fiction: Breathalysers are 100% accurate.

Fact: All commercial breathalyser products can reliably determine if alcohol is present in a breath sample. But the accuracy of breath test results can vary substantially. Breathalyser models are generally divided into two categories: for personal use or professional use. Professional-grade breathalysers offer extremely high accuracy and sensitivity, and employ the same advanced fuel cell sensor technology that is used by law enforcement for roadside alcohol testing. Because prices for fuel cell devices have come down in recent years, they are increasingly popular for personal use. Breathalysers that use semiconductor sensors are usually associated with personal use. All breathalysers must be calibrated periodically in order to maintain accuracy, and failure to do so can affect BAC readings.

Fiction: Breathalysers only measure alcohol – and nothing else.

Fact: Substances that contain small amounts of alcohol can produce false positives, for example some mouthwashes and toothache medicines. In addition, some personal breathalysers may measure compounds that are similar in molecular structure to alcohol, such as acetone, which is present in the breath of diabetics and persons on high protein diets. False results can also be triggered by paint fumes, varnish, cleaning chemicals that contain rubbing alcohol, and some plastics and adhesives.