A Breathalyzer is a drunk driving detection tool used by law enforcement to test for drunk driving without taking blood or some other fluid. In other words, it’s a way for the police to test for a impaired driving with minimal intrusion – or less intrusion than taking your blood or other fluids.
The breathalyzer gives a reading based on the blood alcohol level in 100 mL of blood. In British Columbia, a result of .08 or higher is considered impaired driving and will likely result in a DUI charge. However, also in B.C., in some circumstances, a police officer may issue a 24 hour ticket instead of making an arrest on the criminal charge of DUI.
A police officer must have a reason to ask a driver to blow into a breathalyzer. Good enough reasons include (but are not limited to) smelling alcohol, slurred speech, poor performance during a roadside sobriety test, and any other signs of impairment. The reason an officer must have a reason to force you to blow into a breathalyzer is Canadian law protects the individual right against unreasonable search and seizure (section 8 of the Canadian Charter of Rights and Freedoms). Note that refusing to blow into a breathalyzer is criminal offense in itself.