While operating a car, there is no tolerance for the presence of narcotics in your saliva or blood.
Drugs can be discovered long after you have used them, and even if you do not feel affected, it is assumed that you are unable to drive a motor vehicle safely, or that you are driving less safely, regardless of the amount of the following drugs in your system:
If a driver's saliva test yields a positive result, indicating the presence of an illicit substance, the police officer will ask the driver to take a second test, which, if positive, will be sent to a laboratory for confirmation.
The lab results are what is utilized as the basis for the drug driving charge.
The length of time an illicit substance stays in your system varies based on the type of drug, the amount consumed, and the frequency with which it was consumed.