What do we have to call it?

Navy: "Black Gang"

The black gang are the members of a ship's crew who work in the fire room/engine room;[1] they are also called stokers or firemen.[2] They are called "black" because of the soot and coal dust that is thick in the air in the fire room/engine room. The term began being used in the days of the coal-fired steamships. The term is commonly used in the United States Coast Guard and United States Navy to describe personnel in "M" and "B" divisions.