If you have wasps you will more than likely notice a huge influx of them around or near the suspected area. You may also actually see the wasp nest, if not you will notice the wasps coming in and out of a certain area. Wasp are one of the biggest pests in summer time but they are also very easy to remove!
I can remove wasps in only one visit guaranteed. This is done with a powder insecticide that is sprayed over the nest and directly affects the pests.
Are you having problems with wasps/wasp nests in your home loft hedge or work?