"To begin with, the
NFL's threshold for THC levels is 15 nanograms per milliliter, compared to a 50 ng/ml level used by the U.S. Military and MLB, and a 150 ng/ml level used by the World Anti-Doping Agency, which oversees the Olympics. Although the NFL's level is too stringent to begin with, its testing policy is even worse."
For Gordon, the "A" bottle showed a concentration of 16 ng/ml, only one nanogram per milliliter above the limits of 15. The "B" bottle showed a concentration of 13.6 ng/ml — less than the threshold.
Read more:
http://www.businessinsider.com/nfl-drug-testing-policy-2014-7#ixzz3QFBui93E
If the labels on his samples had been reversed he would have passed the test.
"The results,
published this month in the Journal of Analytical Toxicology, gives nonsmokers with weed-using friends reason to breathe easy. The scientists found urine levels of this metabolite surpassed typically detectable levels (50 nanogram per milliliter) in only one experiment participant, and this happened during a brief window four to six hours after exposure.
Using a more sensitive test, however, which is not usually employed in the workplace,
scientists could detect blood THC levels above the 20 nanogram per milliliter in several participants in the hours after exposure. But these concentrations dipped below this threshold for all participants within 24 hours, according to the study, conducted by researchers at the Johns Hopkins University School of Medicine and elsewhere."
http://www.newsweek.com/could-second-hand-pot-smoke-make-you-fail-marijuana-test-278913