A lot of the people that opt for air duct cleaning do so for the purposes of getting rid of dust and debris from their air ventilation systems, but there is a pretty good chance that mold is a major concern for you as well. Having mold spores coming out of your air ducts can be a nightmare for anybody, so it makes a lot of sense that you would be anxious to start collecting air samples to check them for mold just in case the cleaning process was not able to get the job done in a reasonable enough manner.
The truth of the situation is that when you go wholesale you can get some high end equipment to clean your air ducts with, but checking for mold is still important. This is because of the fact that mold is one of the most stubborn things that you will ever have the misfortune of having to deal with, and you should be wary of anyone that tells you otherwise. Checking for mold too soon after cleaning will spoil the results since they would have no chance of being all that accurate at all.
Instead, the fact of the matter is that you should try to wait at least twenty four hours. This will help everything settle in the freshly cleaned air ducts after which you can turn your ventilation system back on with ease. The sample that you get will be a very accurate representation of the state of your air quality, and if you notice any mold you can start cleaning it again to get it out.