Which of the following is NOT a type of sample used for drug testing?

The correct answer is vapor, as it is not a recognized type of sample used for drug testing. Drug testing typically involves analyzing biological samples to detect the presence of substances. Common examples of these samples include saliva, urine, and hair.

Saliva tests are used for their non-invasive nature and can provide a quick assessment of recent drug use. Urine is the most widely used sample for drug testing, as it can detect a broad range of substances and is generally cost-effective and reliable. Hair tests offer a longer detection window, allowing for the identification of drug use over months instead of days or hours.

In contrast, vapor is not a standard sample type for drug testing. While it's true that substances can exist in vapor form (as in the case of inhaled drugs), the collection and analysis of vapor would present significant challenges and is not currently a recognized or practical method for drug testing. This distinction underscores the established methodologies used in the field of drug testing, focusing on biological samples that can reliably indicate consumption and presence of substances in the body.