Class 6 dangerous goods cover two different hazards under one heading: Division 6.1 toxic substances and Division 6.2 infectious substances. Both require careful classification before a shipment reaches a carrier — getting the paperwork wrong can mean a shipment refused at an airline counter or held at a freight dock. This guide covers how each division is classified, packaged, and documented, and where South Florida shippers moving product through MIA cargo or the seaports run into trouble.
Division 6.1: Toxic substances
Division 6.1 covers substances known or expected to cause death or serious injury if swallowed, inhaled, or absorbed through the skin. This broad category includes pesticides, certain industrial chemicals, some pharmaceuticals, and cyanide compounds, among others.
Packing groups
Toxic substances are assigned one of three packing groups based on oral, dermal, or inhalation toxicity data (LD50/LC50 values):
- Packing Group I — high danger, the most severe toxicity thresholds
- Packing Group II — medium danger
- Packing Group III — minor danger, the least severe thresholds that still meet Division 6.1 criteria
The packing group drives which UN-specification packaging performance level is required and, in some cases, which quantity limits apply for air or vessel transport. For a deeper look at how packing groups are derived, see our breakdown of packing groups PG I, II, and III.
Inhalation toxicity zones
Gases and volatile liquids that meet Division 6.1 criteria by inhalation route are further divided into inhalation toxicity zones (commonly referenced as Zones A through D for liquids, with a similar concept for gases). These zones reflect how readily a substance forms a hazardous vapor concentration and factor directly into packing group assignment and, for some materials, whether air transport is permitted at all. Zone assignment depends on vapor pressure and LC50 data and should be confirmed against current test data or a safety data sheet, not assumed from a product’s general reputation.
Packaging and segregation from foodstuffs
Division 6.1 materials must ship in packaging that meets the UN performance standard for the assigned packing group, properly marked and tested for the mode of transport used. Segregation is a recurring compliance point: 49 CFR and the IMDG Code both restrict loading Division 6.1 materials in the same transport unit as foodstuffs unless the toxic substance is further contained (overpacked) to eliminate the contamination risk. This comes up often for shippers consolidating LTL freight, where a toxic substance and a food-grade product can end up on the same truck unnoticed. Reviewing current hazmat segregation rules for ground transport before freight is tendered is more reliable than relying on a driver to catch it.
Division 6.2: Infectious substances
Division 6.2 covers materials known or reasonably expected to contain pathogens capable of causing disease in humans or animals. It has its own packaging system, largely because the industry — and IATA in particular — has built out detailed guidance for clinical and laboratory shipments.
Category A vs. Category B
| Category | UN number | Definition |
|---|---|---|
| Category A | UN2814 (humans) / UN2900 (animals only) | Capable of causing permanent disability, life-threatening or fatal disease in otherwise healthy humans or animals |
| Category B | UN3373 “Biological Substance, Category B” | Does not meet the Category A criteria; the common classification for routine diagnostic specimens |
Category A shipments carry far more restrictive packaging, documentation, and carrier acceptance requirements than Category B, and many carriers will not accept UN2814 or UN2900 without advance coordination. Confirming which category applies is the single most consequential decision in shipping an infectious substance.
Triple packaging
Both categories rely on a triple packaging system: a leak-proof primary receptacle holding the specimen, a secondary packaging (also leak-proof, with absorbent material between the layers), and a rigid outer packaging. Testing requirements differ between Category A and Category B outer packaging, so a Category B box is not automatically acceptable for a Category A shipment. Shippers needing help sourcing compliant packaging often work with a provider that handles hazmat repacking and UN-spec packaging.
Exempt human and animal specimens
Specimens with a minimal likelihood of containing pathogens — most routine blood work or diagnostic samples from patients without a known infectious condition — may qualify as exempt human or animal specimens under 49 CFR 173.4b and the equivalent IATA DGR provision. Exempt specimens still need packaging that prevents leakage and marking as “Exempt human specimen” or “Exempt animal specimen,” even though they fall outside the full Division 6.2 package. The exemption depends on the shipper’s knowledge of the source and must be documented, not assumed.
Dry ice as a co-shipped refrigerant
Many Category B and exempt specimen shipments travel on dry ice to keep the sample at the required temperature in transit. Dry ice (UN1845) is itself a regulated material — classified as Class 9 when shipped as a refrigerant — with its own quantity limits, marking requirements, and package venting considerations that stack on top of the Division 6.2 requirements for the same box. This is a frequent point of confusion because the specimen and the dry ice are documented and marked separately even though they move in the same package. South Florida shippers sending specimens through MIA cargo can source properly packaged dry ice locally rather than well in advance; see our South Florida dry ice supply and delivery service for same-region options.
A South Florida angle
Miami’s position next to MIA cargo, PortMiami, and Port Everglades means a lot of Class 6 freight moves through the region — pharmaceutical and diagnostic shipments to and from Latin America and the Caribbean, chemical shipments through the ports, and specimen shipments tied to South Florida’s medical and research sector. That volume means carriers and forwarders in Miami-Dade and Broward are generally used to the documentation, but familiarity cuts both ways: it’s easy to assume a shipment is handled correctly because “we ship this every week,” when packing group, category, or dry ice quantity has quietly changed.
Frequently asked questions
What is the difference between Category A and Category B infectious substances?
Category A substances can cause permanent disability or life-threatening or fatal disease in otherwise healthy humans or animals and ship as UN2814 or UN2900. Category B substances do not meet that threshold and ship as UN3373, “Biological Substance, Category B.” Category A shipments face stricter packaging and carrier acceptance requirements.
Can I ship dry ice and a Division 6.2 specimen in the same box?
Yes, dry ice is commonly used as a coolant for infectious substance shipments, but it is regulated separately as UN1845 and must be documented, marked, and quantity-limited in addition to the Division 6.2 packaging and marking for the specimen itself.
Does a toxic (Division 6.1) shipment need special handling around food products?
Generally yes. 49 CFR and the IMDG Code both restrict transporting Division 6.1 materials with foodstuffs unless the toxic substance is further contained in a way that removes the contamination risk. Segregation requirements should be checked for the specific mode of transport and current regulatory edition before loading.
Regulations under 49 CFR, the IATA DGR, and the IMDG Code are revised regularly. This article reflects general classification concepts and is not a substitute for checking the current edition applicable to your shipment. For shipment-specific support, contact our team or request a quote.