We get many calls in November about “wasps in the house”. During the summer months wasps make their nests in caps of chimneys that haven’t been used for awhile. This is especially true for those chimneys that vent gas logs.
Wasps love chimney caps. Chimney caps protect them from the elements and allow the wasp to move in and out through the screen. It is a great environment for wasps.
As the weather cools the wasps move down the chimney flue (pipe) to seek a warmer area. In the Southeast US they are down by the damper when Thanksgiving rolls around. You open the damper and groggy wasps fall into the fireplace, and fly all over the room.
Prevention from wasps in the house in November is to burn two or three fireplace fires in October, while the wasps are still up high. Wasps will feel the heat and move out of your chimney cap. Do it, you will be glad you did.