  We consider the coagulation-decoagulation model on an one-dimensional lattice
of length $L$ with open boundary conditions. Based on the empty interval
approach the time evolution is described by a system of $\frac{L(L+1)}{2}$
differential equations which is solved analytically. An exact expression for
the concentration is derived and its finite-size scaling behaviour is
investigated. The scaling function is found to be independent of initial
conditions. The scaling function and the correction function for open boundary
conditions are different from those for periodic boundary conditions.
