Abstract: Reasonable inerting design can guarantee the safety of a process to treat combustible materials and save running cost. The measurement and test apparatus of limiting oxygen concentration (LOC) of combustible dusts were introduced with the LOC of some conventional combustible dusts given. Assuming that the gas is mixed homogeneously, the calculation methods of inerting times using pressure-swing inerting and vacuum-swing inerting, and the inerting time using flow-through inerting were deduced. An empirical formula was given for determining the minimum inert gas flow rate. An example of inerting design was given for a pulverized coal drying process, where the inert gas flow rate can be estimated by recycled air flow rate and air leaking rate. When shut down for a short time, a lower inert gas flow rate (1 or 2 equipment volumes per hour) can be used to maintain inert atmosphere.