Are you clean of THC after 16 days?

The short answer:
Probably not.

The long answer:
THC is stored in your fat cells and is metabolized over time. These metabolites are present and can be detected in your blood, hair, urine, or saliva. Because your body metabolizes THC at a constant rate, the amount of time it takes to rid your system of it all depends on various factors. These factors include, but are not limited to:
- Metabolic rate
- Amount of THC ingested
- Amount of body fat
- Frequency of THC intake.

Let me put this another way. Picture your body as a gallon jug of water with a tiny hole in the bottom allowing a small stream to leak out. Now picture putting a drop of red dye in the bucket. This is your THC. It will disperse quickly and is virtually undetectable. What if you put a drop in every hour? Maybe a slight color change, but over-all it's the same.

Now let's say you put a cup of red dye in the water every hour. The jug cannot let out all of the red dye before you put more in, thus prohibiting you from a clear stream.

With this information in mind, your best chances of passing a drug test are to stop smoking, eating, or vaporizing your herb as soon as you know there is a test coming up. If you fail, don't deny it. The facts are in your pee and a false positive is very rare.