Finding carpenter ant nests requires a lot of time an patience. With years of experience, a professional will know where these nests are likely to be and will look for evidence of frass, the junk thrown out of nests. This is often caught up in spider webs in attics, crawl spaces, basements under decks and around the exterior perimeter under the soffits and below the siding. Sometimes sawdust excavated by the ants from the structure will be noticeable, but not always.
Following ants outside the nest is the best
indication of it's location, but ants will often follow channels hidden from the
hot sun, rain and your vision. Less than 10 % of the population will ever
leave the nests so at times there are very few to follow. Knowing whether the
ant you are following is heading for food, or has already eaten and is heading
back to the nest is an indicator that some very experienced professionals are
capable of seeing.