FIBC Electrostatic: Why Type C Bags Target One Discharge Type

Not every static discharge carries the same ignition risk, and understanding the difference is what actually explains why Type C construction exists as a distinct category rather than just a stronger version of Type B. This guide goes into the mechanics behind electrostatic hazards in FIBC handling, the different discharge types and their relative danger, and how hazardous area zone classification determines what protection level a facility actually needs.

How Triboelectric Charging Actually Generates Static in Powder Handling

Static charge builds up through triboelectric charging, the transfer of electrons between two materials in contact as they separate, which happens continuously as powder or pellets flow against each other and against bag fabric during filling, pneumatic conveying, and discharge. The rate of charge generation increases with flow velocity, meaning high-speed filling and pneumatic transfer systems generate meaningfully more static than slow, gentle handling of the same material.

Read more: FIBC Bags for Plastic Resin: PP Fabric Packaging PP Pellets

The Four Discharge Types and Their Relative Ignition Energy

Accumulated static charge releases through one of several distinct discharge mechanisms, and these differ substantially in how much energy they carry and, correspondingly, what they’re capable of igniting.

Discharge Type	Relative Energy	Practical Relevance
Corona discharge	Very low	Generally insufficient to ignite most dust or vapor atmospheres
Spark discharge	Can be significant	From an isolated conductor, capable of igniting many flammable atmospheres
Brush discharge	Low to moderate	Can ignite some flammable gas or vapor atmospheres but typically not dust
Propagating brush discharge	High	Capable of igniting dust clouds, the specific hazard Type C construction addresses

Why Propagating Brush Discharge Is the Hazard Type C Bags Specifically Address

Propagating brush discharge occurs specifically with thin, highly insulating materials that have a high breakdown voltage, conditions that ungrounded or poorly designed FIBC bags can create. This discharge type carries enough energy to ignite combustible dust clouds, which is why standard bags handling fine flammable powders present a genuine risk that lower-energy discharge types don’t. Type C construction eliminates this specific risk by providing a grounded conductive path that prevents the high-voltage buildup propagating brush discharge requires in the first place.

Read more: Anti-Static Bulk Bags: How a Type C Bag Prevents Ignition Risk

ATEX Hazardous Area Zones and What They Require

Facilities handling combustible dust are classified into hazardous area zones based on how frequently and for how long an explosive dust atmosphere is likely to be present, with Zone 20 representing continuous or frequent presence, Zone 21 representing occasional presence during normal operation, and Zone 22 representing presence only under abnormal conditions. This zone classification, established through a facility’s own hazard assessment, is what actually determines whether Type C, Type B, or standard construction is appropriate, rather than the FIBC bag choice driving the classification.

Matching Bag Type to Your Facility’s Zone Classification

Zone 20 areas generally require the most rigorous static control, making properly grounded Type C construction a standard expectation.
Zone 21 areas commonly also call for Type C protection, particularly where dust clouds form during routine filling and discharge operations.
Zone 22 areas may be adequately served by Type B construction depending on the specific dust’s minimum ignition energy, though this should be confirmed against the facility’s formal hazard assessment rather than assumed.
Areas outside any classified zone, handling genuinely non-combustible material, may not require static protection at all.

Read more: Dust Proof Bulk Bags: Controlling Exposure Standard Sift Proofing

Common Electrostatic Hazard Misconceptions

Assuming any anti-static label means the same level of protection, when Type B and Type C address genuinely different discharge mechanisms.
Believing an ungrounded Type C bag still provides meaningful protection, when its conductive grid with no ground connection can actually behave like an isolated conductor.
Assuming zone classification is the packaging supplier’s responsibility to determine, when it’s fundamentally a facility-level hazard assessment the buyer needs to establish first.
Treating corona discharge risk the same as propagating brush discharge risk, when their ignition capability differs substantially.

Building a Complete Electrostatic Risk Assessment

A complete assessment starts with the facility’s own hazardous area zone classification, then confirms the specific product’s minimum ignition energy and whether flammable vapors might be present alongside dust, before determining whether Type B, Type C, or standard construction is appropriate. This assessment should exist independent of, and prior to, any specific bag order, since it’s a facility safety requirement rather than a packaging specification detail.

Read more: FIBC Bags for Chemicals: Building the Right Bulk Bag Specification

How Tam Tam Packaging Supports Electrostatic Hazard Compliance

Tam Tam Packaging manufactures Type B and Type C FIBC bags tested to IEC 61340-4-4, with grounding tag placement and conductive grid design confirmed against the buyer’s stated hazard classification. We work with buyers to understand which zone and discharge risk applies to their specific handling process before finalizing a construction recommendation.

IEC 61340-4-4 static discharge testing on FIBC bag

Frequently Asked Questions

What is triboelectric charging?

The transfer of electrons between two materials in contact as they separate, which is how static charge builds up continuously as powder or pellets move against bag fabric during filling and handling.

Why does propagating brush discharge matter more than other discharge types for dust hazards?

It carries enough energy to ignite combustible dust clouds, unlike lower-energy discharge types such as corona discharge, making it the specific hazard Type C construction is designed to prevent.

What are ATEX hazardous area zones?

A classification system based on how frequently an explosive dust or gas atmosphere is likely to be present at a location, which determines what level of static protection and other safety measures are required.

Who determines whether a facility needs Type C bags?

The facility itself, through its own hazardous area zone classification and hazard assessment, which the FIBC specification should then be matched to rather than driving the assessment.

Does an ungrounded Type C bag still offer some protection?

Not reliably. An ungrounded conductive grid can behave like an isolated conductor capable of accumulating and later discharging its own static charge, which can be as risky as using a standard bag.

Conclusion

Electrostatic hazard in FIBC handling comes down to which discharge type a given situation can produce and how much ignition energy that discharge carries, with propagating brush discharge being the specific high-energy risk Type C construction addresses. Matching bag type to an actual facility hazard zone classification, rather than defaulting to a generic anti-static label, is what makes the protection meaningful.

Tam Tam Packaging Co. manufactures Type B and Type C FIBC bags matched to your facility’s hazardous area zone classification. Contact our team to work through the right electrostatic protection for your application.