The safety verification of chemical processing systems becomes more difficult due to their complexity. Current search methods suffer from the state explosion problem, mainly because the verification problem itself is inherently complex considering numerous units (reactor, distillation column, storage tank), instruments (valve, pump), control software and many other components, and more importantly considering time. This paper focuses on methods of improving the search algorithm in its efficiency. The algorithm enables to prune out the state transition paths that cannot happen in the behavior of process equipment and operating procedures in system modeling. The state transition structure constructed by this algorithm becomes enormously smaller in its search space. Computing time is also reduced and safety verifications of more complex processes and operating procedures become possible.