<P> Saliva / oral fluid - based drug tests can generally detect use during the previous few days . Is better at detecting very recent use of a substance . THC may only be detectable for 2--24 hours in most cases . On site drug tests are allowed per the Department of Labor . </P> <P> Detection in saliva tests begins almost immediately upon use of the following substances, and lasts for approximately the following times: </P> <Ul> <Li> Alcohol: 6 - 12 h </Li> <Li> Marijuana: 1 - 24h </Li> </Ul> <Li> Alcohol: 6 - 12 h </Li>

When did urine toxicology and blood testing start