In addition to licensing, you should perform a thorough background check on the company. According to heating and air durham, you should examine whether there are disciplinary actions or complaints pending against the contractor. You can check these facts with the Better Business Bureau by entering the name of the company into the appropriate fields. Also, you can check with the local or state licensing boards.
Another way to check the company's credibility is to ask for references. Once you have received this list of names of prior customers, follow up. Prior customers will be more than happy to share with you their experiences with a contractor, especially if such encounters have been less than positive. If the general consensus among these prior clients is negative, take your business elsewhere.