Hair drug screening
Hair testing is rather exact and can go back 6 months or longer. It shows any substance used in a sort of timeline. The longer hair you have, the longer back in you drug history the lab can detect any drugs used cause they are concentrated in the hair shaft. Most of the testing facilities use hair with a high just about 3-5 cm of the scalp and discard the rest. This hair high detects the history of using drugs about 2 months, depending upon the rate of growth of the individual's hair. Someones attempt to circumvent this through shaving their heads. In the absence of the required amount of hair on the scalp, body hair can be used as an acceptable substitute. Additionally, for pre-employment hair testing, the inability to obtain a sample may be grounds for not hiring the individual.

Saliva drug screening / Oral fluid-based drug screening
Saliva drug screening tests can commonly detect drug using  during the previous few days. Oral fluid-based drug screening tests are becoming very popular because of their convenience and the fact that they can not be adulterated. Oral fluid based tests are as exact as urine test  and can be got from quality suppliers in the United States. Testing is usually practiced by employers, for either pre-employment, post-accident,  reasonable suspicion, random or return-to-duty testing. Saliva drug screening test most closely mimics results found with blood. It is preferred for detecting drug using at the work plase. Oral fluid based tests usually detectes the post-accident applications because the degree of intoxication can be   approximated based on the amount of substance in the blood.
Detection in saliva tests begins immediately upon use:
• Marijuana and hashish: 1 hour after ingestion for up to 14 hours.
• Cocaine (including crack): from time of ingestion for 48 to 72 hours.
• Opiates: from time of ingestion for 48 to 72 hours.
• Methamphetamine and ecstasy : from time of ingestion for 48 to 72 hours.

Sweat drug screening
Sweat tests are patches attached to the skin to gather sweat over a period of 10-14 days. These are almost solely used by parole departments,  child protective services and other government institutions concerned with drug use over long periods when urine testing is not practical. The patches have confidence characteristic that keep them from removing and then reapplied without the knowledge of the testing agency. When the testing period ends the patch is removed by a social worker or parole officer and is sent to a lab for analysis. If the one who was tested has used any drugs during the period that the patch was in place, he(she) will give positive test for that drug. This type of testing has fallen out of favor with government agencies due to documented problems with certain drugs.