The purpose of an air gap is not really to allow air to escape but rather to keep dirty water from back flowing into the DW. An autovent allows air into the system to allow for proper drainage and an air gap is not dependant on one or vice versa. The autovent takes the place of a vent stack to the roof.
Sudan is a member of the United Nations, the African Union, the Arab League, the Organisation of Islamic Cooperation and the Non-Aligned Movement, as well as an observer in the World Trade Organization. Its capital is Khartoum, the political, cultural and commercial centre of the nation.
The Nile is considered the biggest geographical feature in Sudan. The Nile is the longest river in the world. The White Nile and the Blue Nile meet in Khartoum Sudan's capitail, forming the Nile. The Nile flows to Egypt (Geography of Sudan, 2011). Here is a list of other bodies of water in Sudan: