A digraph is called singular or nonsingular according as its adjacency matrix is singular or nonsingular. An expression of the determinant of the adjacency matrix of a digraph in terms of the determinant of smaller digraphs obtained from the given one is called a reduction formula. Reduction formulas are established in this paper. Furthermore, using these reduction formulas, we determine which of the directed fans are singular. Moreover, we show that if a directed fan Fn is nonsingular, then the determinant of its adjacency matrix is (-1)n.