DOT only allows urine testing. Other testing methods such as hair, saliva, blood and sweat aren't allowed, although the company may also elect to perform an additional test under its own authority (nonDOT) which may be any of the above methods and may screen for the presence of additional drugs. More companies are electing to do this, especially in prehire situations as there are several drugs, both prescription and illicit that may cause a problem in performing safety-sensitive duties that the DOT test simply will not pick up such as Oxycodone, Methadone, Vicoden etc.
If you're going for a CDL and trucking, then you fall under the purview of the Federal Motor Carriers Safety Administration (FMCSA). The rate of Random drug testing is set at a minimum of 50% of covered employees (this would include you as a driver) in a given period depending on how the company pulls their random draws - most companies generate a list either monthly or quarterly. So in any given period, you have at least a 50% chance of being selected. Each new period, everyone goes back in the pool and the selection process begins anew, so someone may be tested on 3 consecutive periods while their buddy may not be tested at all. Keep in mind that this is a minimum rate, the company may test all safety-sensitive individuals in every testing period. Very few, if any do however, mainly because of cost. The random pull has to be statistically random - this is one of the things that DOT auditors may ask to see proof of in the event the company is audited, so any issues with that any established company may have had in the past will likely have been ironed out long ago. Also, many companies hire the services of a TPA to generate the lists for them.
Most if not all detox products are a complete waste of money. You would do as well to just drink a gallon or so of water in the hours leading up to the test if you're worried about passing. It's not surefire, but it's your best chance unless you go for the substitution method. Labs aren't required to test for any products that you may take orally before giving the sample, therefore they don't. They simply test for certain adulterants (Nitrites) that may have been added to the sample after peeing in the cup before giving it to the collector in an attempt to mask the presence of drugs.
The idea with dilution is to drop the concentration of THC metabolite in your sample to 14ng/mL or below (GC/MS confirmation cutoffs on DOT samples is set to 15ng/mL, so at or above that number you'll be positive), but doing it without diluting too much which will result in an "invalid" result and the test being cancelled with a requirement for an observed recollection. Assuming the temperature of the sample is within normal range and you didn't try and bring anything to the collection site that may be suspicious, and there's no foaming, abnormal odor or particulates in the sample, the collector CANNOT tell you the sample is "too clear" or "invalid" at the collection site and make you take an observed test immediately. That's up to the lab and the MRO.
Once you've taken the test your sample will be sent to a lab. Depending on when the sample gets picked up from the collector and lab backlog, your company should have a passing test within 48-72 hours or so. If it goes to confirmation testing or the MRO needs to review it, it will likely take longer. It's advisable to abstain from smoking for as long as you can before the test and not to start again before you have confirmation from your boss or the person that's hiring you that they have the negative (I've heard several stories about people who stopped smoking for weeks before the test, then smoked a blunt after leaving the collection site and then had to go back for another test for one reason or another
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Once you're (hopefully) hired, then it really is a lottery with the Random pulls.
Hope this helps.
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