I was recently told duct cleaners don't have to be licensed to clean my vents. Is that true ?
No it is not true. The State of Michigan does require companies that come into your home to clean your system to be licensed.  There are specific license categories required to perform different tasks on different components of your system.  These categories fall under the Mechanical license that the State issues after testing is completed and passed.  I will list out these categories and explain what each one allows the service provider to do in your home according to State ordinances.  These are the minimum required categories.

Category 3:  Ductwork.  Allows for accessing the duct work by means of cutting holes to attach suction piping and for entering agitation tools.

Category 5:  Limited heating service.  Allows for opening up the furnace for cleaning, removing and replacing filters, cleaning blower wheels or any component of the furnace.  The State classifies 'cleaning ' as service.

Category 7: Limited refrigeration/AC service.  Allows for accessing and cleaning the evaporator coil that is part of your Air Conditioning system and sits on top of your furnace. Again the State considers 'cleaning' as service.

Some duct cleaning companies think that they are only required to have category 3 on their Mechanical license. Some don't have any license at all. The State of Michigan does have a position paper on this issue that clearly states that those listed categories are required of all duct cleaners who will be directly accessing the duct work, cleaning the furnace or any A/C system component.

What does all this mean to you the homeowner or the business owner?  The answer is Liability.

The State doesn't appear to be able to police this activity at this time but there are those that do. Insurance companies. They are concerned about unlicensed companies going into their insured properties. If you allow a service company without the proper license , or the required classifactions on their license, to perform service in your home or business, you are opened to unlimited liability. For instance if your home should burn down and the fire is traced back to the furnace after you  had an unqualified service company clean it,  your insurance company doesn't have to honor your claim.

There certainly are other reasons to insist on proper licensing from a service company besides a disaster like a fire. We all want qualified people working on our cars, homes and ourselves. I would never go to an unlicensed Doctor because he was cheaper. In life you always get what you pay for.