Observation:
Before administering the preliminary breath test, it must be determined that the subject has not smoked, regurgitated or placed anything in his/her mouth for at least 15 minutes prior to the test. Also check to ensure there are no signs of injury or blood in the subject’s mouth. This 15-minute period ensures any residual mouth alcohol that could possibly be left in the subject's mouth if the subject had just finished drinking prior to the test will not affect the results.