An experimental investigation was carried out to determine the reasonable upper limit of resistance of the Type C flexible intermediate bulk container (FIBC). Using custom-made FIBCs, of which the resistance to the groundable point was adjusted from 10(4) to 10(8) Omega, the discharge current waveforms were measured when the FIBC was given static charges. Ignition tests by the discharge from the FIBC, using a flammable test mixture, were also performed. In addition, the incendivity of the discharge from the FIBC was carefully evaluated with an ignition test apparatus that was able to simulate discharges from the FIBC. As a result, the incendivity of the spark was reduced as the resistance of the discharge circuits increased. It was found that an ethylene-air mixture with a minimum ignition energy of less than 0.1 mJ can be ignited when a heavy-duty FIBC with a resistance of 1 x 10(8) delta is charged more than equal to 15 kV. It is concluded that a heavy-duty Type C FIBC of slightly less than 1 x 10(8) Omega is quite unlikely to ignite flammable gas or vapor during filling and emptying operations because it reaches as high as 3 kV even when an unrealistically large static current of 30 mu A flows into the FIBC, as long as it is properly earthed. It should be noted that if the FIBC is not properly earthed, the possibility of ignition increases with a lower resistance of the FIBC.