How Breathalyzers Work

When alcohol is consumed, it is carried into the bloodstream by being absorbed through the mouth, throat, stomach and intestines; because of this, it is detectable in the breath of the consumer. Blood alcohol content (BAC) can be tested by measuring the alcohol level present in a consumer’s breath, allowing officers to administer a roadside breath test rather than acquiring a blood sample.

When consumed, alcohol is neither digested nor chemically changed when it enters the bloodstream. When blood travels through the body, some of the alcohol passes through the membranes of the lungs’ air sacs, and exits the body through air that is exhaled. Because of this process, the concentration of alcohol exhaled through breathing is related to the concentration of alcohol present in the bloodstream and can be detected using a breathalyzer device.

The ratio of alcohol present in a person’s breath, to alcohol present in their bloodstream is 2100:1, meaning that 2100 mL of air will contain the same amount of alcohol as 1 mL of blood.

Blood Alcohol Content and DUI Charges

Most Canadian provinces have set a 0.08 BAC as a common standard for issuing an impaired driving charge. While this is the case for many provinces, the American Medical Association claims a person can become impaired when they reach a BAC as low as 0.05. Because of this, provinces such as Alberta and British Columbia have implemented a sub-category of DUI laws that deal with drivers with BACs between 0.05-0.08.

BAC Testing Devices for Impaired Driving

Alberta’s law enforcement officers use two types of breath-alcohol testing devices:

Alco-Sur (a portable roadside screening device that delivers an informal BAC reading)
Breathalyzer (a machine that calculates an exact BAC reading)

Both of these devices have a mouthpiece through which air is blown into a chamber that then calculates the blood alcohol level of the suspected impaired driver.

The Breathalyzer Device

Every breathalyzer device contains:

  • A system to collect the breath sample
  • Two glass vials containing chemicals that react to alcohol
  • Photocells that measure the colour change associated with the chemicals’ reaction to alcohol

The Science Behind a Breathalyzer Test

When you breath into a breathalyzer, the air you exhale is combined with a mixture of sulphuric acid, potassium dichromate, silver nitrate, and water. These chemicals remove alcohol from the air and into a liquid solution, and change colour depending on the amount of alcohol present in the solution. The amount of alcohol in the breath sample is determined by comparing the reacted sample to an unreacted mixture in the photocells. An electric current passes through the reacted mixture, which causes a meter-needle to move, the person operating the breathalyzer then rotates a knob to bring the needle back to its original position –the more alcohol present in the sample, the more the operator must turn the knob.

Contact our DUI Lawyers in Fort McMurray if You Have Been Charged with Impaired Driving

If you have been charged with impaired driving following a breathalyzer test, and are now facing a license suspension or other DUI related penalties, contact the lawyers at Gunn Law Group. Our experienced team of DUI lawyers will review your case and help to minimize the damaging effects of an impaired driving conviction.