Officers were called to a house on Coronation Terrace in the New Kyo area of Stanley at about 9.15pm on Monday (February 13) night.
Concerns were raised about the welfare of a man, 51, and a containment area was erected around the house.
Trained negotiators have been speaking to the man and remain at the scene this morning.
Roads in the area are currently closed and people are being asked to stay away from the area.
Durham Police said: “Roads surrounding the property are closed and people are asked to avoid the area for the foreseeable future.
“We would like to thank local residents for their patience and understanding while we work at the scene.”