People rarely think of the need to have their air ducts cleaned out. They shall keep on working as well as expected, until you have someone over who has allergies. Cleaning the ducts then becomes a matter of urgency. You need to entrust such work to a company that knows what experience and skills are needed. This is not work to be assigned to just anyone. You will have to identify the right service providers when such work has to be done.
The best place to begin your search is to look at what air duct cleaning companies are based in the area. There is usually no shortage of such service providers in any given area. If they are not near, you should make a point of searching for those that cover those distances to your region. You can then look at hat different companies have to offer to you.
You need to know what charges come with the requested cleaning services. This is necessary before you commit yourself to a specific service provider. They usually, look at the duct area to be cleaned and the number of skills to be applied in doing so as they make their charges. This is why you need to find out what you shall be getting in return to the amounts you are about to spend, as per your estimates. There is also the internet, which has simplified the process of getting such estimates done for you. You need them to also pay a visit, to get a more detailed assessment done after they see the work that awaits them. They will also use this trip to gauge the amount of work that needs to be done, and the techniques most suited for that kind of work.
You need to then ask for references from their previous working. This will be how you gauge their preparedness to do such work, or lack of it. By also looking at their testimonials and reviews, you will know whether they are able to deliver what they have promised.
When you have assessed their credentials and reliability, you will have to decide which among the shortlisted are to deliver the needed services. It is important to ask them what they intend to do, and if they have a plan for it. They need to also provide a good period of time in which they expect to be done. You need to see a reasonable timeframe for this. Some service providers have been known to drag such work for unnecessarily too long.
When you approach the task this way, finding someone to do a good job will not be hard.