Can Secondhand Marijuana Smoke Cause a Failed DOT Drug Test? The Science and the Defense That Second hand vaping exposure very low compared to second hand smoking UCL News UCL University College London Safe & Responsible Consumption Thirdhand Smoke Resource Center Protecting Californians Can You Fail a Drug Test from Secondhand Smoke? Understanding the Facts Even if an employee only uses marijuana on the weekends, it could still show up on their workplace sponsored drug screen the following week or later. According to some estimates, traces of THC