Buying it isn't always a sure way, The tech who recives the specimen from you is required to take a temp. reading in the cup right away. And of course the specimen is accompanied by a Chain of Custody form. A positive result will only be reported to your boss after the orignal sample has been tested atleast 2x. Ultimately, pleading "I didn't do it" after the fact will not work, BUT You can find a flaw in the Chain of Custody form, You will recive a copy. Look at dates, signatures, what the chain of release had been for your sample starting with your signature to release it to the Collector. In some states the law recently changed and the collector must be a CPC (Certified Professional Collector)Get educated before your test. Distract the tech from recording the TEMP. or dating or .. something. A flaw in the CoC is the only way to have a result *retracted.
There are some products that do work. Many of those products also produce a "greenish" specimen, which can lead to follow-up testing. If you "smoke"frequently the products won't always work. If you don't partake very often (less than 2x a month) there are often too few THC crystals that have attached to the metabolites in your urine to be reconized by the machine and this is where the products you can buy will help alot. I have used Kw1k caps myself, with success. If you use them, YOU MUST FOLLOW the directions to the letter or it will not work. Most require abstanence for atleast 72 FULL hours, they mean it.