norml seems to be down.

here's the cached version:
Drug Testing Tips - NORML

learn something new every day.

BLOOD TESTS: In some situations, including accidents and roadside sobriety checks, blood tests may be used. Blood tests are a much better gauge of current impairment than urine tests because they detect the actual presence of THC in the system; however, they can be sensitive to other metabolites as well. Blood tests generally register positive for just a few hours after smoking, though heavy chronic smokers may be positive for a couple of days. Less sensitive are saliva tests, which register positive for about 2-4 hours after smoking. If you have used marijuana in the last few days but are not currently under the influence, you should insist on a blood (or saliva) test instead of a urine test if at all possible, since you are more likely to turn up clean. On the other hand, if you have smoked recently, you may do better to take a urine test, since this will at least leave open the question as to whether you were under the influence. Also, urine doesn't turn positive until several minutes after smoking.