Type A, B, C and D are the four electrostatic classes of flexible intermediate bulk containers (FIBCs), and the letters describe how much protection the bag gives against static discharge during filling and emptying. Type A has no protection, Type B limits the most dangerous discharges, Type C is conductive and must be earthed, and Type D dissipates static without earthing. The classification is defined in IEC 61340-4-4, and the right type depends on whether your product is flammable, whether flammable solvents or gases are present, and what the receiving site can do.
Any bulk powder generates static as it flows, and a spark inside a dusty or solvent-laden atmosphere can ignite it. The choice of bag type is therefore a safety decision as well as a packaging one, and most importers treat it as part of the risk assessment for the whole filling and discharge process.
The four types
- Type A bags are plain woven polypropylene with no static protection. They are suitable for non-flammable products in an environment with no flammable solvents or gases, which covers the bulk of agricultural, mineral and construction materials.
- Type B bags are also plain polypropylene but use a fabric or coating with a low breakdown voltage, which prevents propagating brush discharges. They do not prevent ordinary brush discharges, so they are not suitable where flammable solvents or gases are present.
- Type C bags are made from fabric with interwoven conductive threads, usually visible as a grid or stripe pattern, connected to an earthing tab. They must be earthed during filling and emptying and are used for flammable powders and for environments with flammable vapours.
- Type D bags use fabric with static-dissipative yarns that bleed charge away safely without any earth connection. They are chosen where earthing is unreliable or impractical, but they are not suitable if the bag surface may become contaminated with water or conductive material.
How to decide
Start with your product's minimum ignition energy and the atmosphere at the filling and discharge points. If neither the product nor the surroundings are flammable, Type A is usually enough and is the lowest-cost option. If the product is flammable but the surroundings are not, Type B or Type D may be sufficient. If flammable vapours are present, Type C with a verified earth connection, or Type D where your safety advisor accepts it, is the normal answer.
Do not rely on the supplier to make this choice for you. Indian FIBC mills can make all four types, but they do not know your site conditions, and the responsibility for the classification rests with the user.
What to check on Indian supply
Type B, C and D bags should come with test reports showing compliance with IEC 61340-4-4, and for Type C the fabric lot should be checked for continuity of the conductive grid. Ask for the label content in advance, because the type marking and any earthing instructions must appear on the bag. A Type A bag mislabelled as Type D is a serious hazard, so the bag type should be verified at the mill and again at pre-shipment inspection.
How Creston & Co helps
We audit the mill, check the electrostatic test reports against your specification and send sealed samples to an NABL-accredited lab where the type claim needs independent confirmation. Pre-shipment inspection covers labelling as well as construction, and we supervise loading at the port. We keep one approved supplier plus one backup, send weekly updates, and begin with a free 20-minute sourcing review.