The term “biological sample” describes an enormous range of materials, but it does not by itself determine how a shipment must be classified for transportation.
Blood, tissue, cell cultures, swabs, microorganisms, animal specimens, diagnostic samples, and research materials may look similar when packed inside a laboratory tube, but their transportation requirements can be very different.
Before a biological shipment moves, one of the most important questions is therefore: What is the material’s correct transportation classification? The answer can determine the packaging solution required, the marks and labels placed on the package, the documentation accompanying the shipment, airline acceptance requirements, and the training required of the personnel preparing it.
Classification should therefore occur before packaging and transportation decisions are finalized.
“Biological Sample” Is Not a Transportation Classification
Terms such as “biological sample,” “research sample,” “laboratory specimen,” or “tissue sample” may describe a material generally, but they do not necessarily establish its regulatory classification for transportation.
The classification process requires more information. Relevant questions may include:
- What exactly is the material?
- Is it of human or animal origin?
- Does it contain a pathogen?
- Is a pathogen reasonably expected to be present?
- If infectious, what level of hazard would exposure present?
- Is the material a culture?
- Is it a patient specimen?
- Has it been fixed, inactivated, purified, or otherwise treated?
- What professional or scientific information is available about the material?
For infectious substances, the distinction between Category A and Category B is based on the hazard presented by the material during transportation—not simply on whether the specimen originated from a human or animal.
Category A: The Highest-Risk Infectious Substances
A Category A infectious substance is an infectious substance transported in a form that, when exposure occurs, is capable of causing permanent disability or life-threatening or fatal disease in otherwise healthy humans or animals.
Category A infectious substances are assigned to one of two UN numbers depending on whom the substance affects: UN 2814 – Infectious substance, affecting humans, or UN 2900 – Infectious substance, affecting animals only. The words “animals only” are important.
UN 2900 applies when the infectious substance affects animals but does not meet the criteria for an infectious substance affecting humans. An animal-origin specimen is therefore not automatically UN 2900. Similarly, a human specimen is not automatically UN 2814.
The classification depends on the infectious substance and the hazard it presents. Category A shipments are subject to stringent packaging, marking, labeling, documentation, training, and carrier acceptance requirements.
Unlike Category B shipments, Category A infectious substances transported by air require a Shipper’s Declaration for Dangerous Goods when applicable under the governing dangerous goods regulations.
UN 3373 Biological Substance, Category B
Biological Substance, Category B is an infectious substance that does not meet the criteria for inclusion in Category A. The UN number is UN 3373, and the proper shipping name is Biological Substance, Category B.
This classification is frequently encountered in clinical, diagnostic, and research shipments involving human or animal specimens. Depending on their characteristics and the likelihood that infectious substances are present, materials such as blood and blood components, tissues, fluids, excreta, secretions, and other patient or animal specimens may fall within Category B.
However, none of these materials should be classified as UN 3373 solely because of what they are or where they originated. A blood sample, tissue sample, swab, or other biological specimen is not automatically Category B simply because it comes from a patient, laboratory, hospital, veterinary facility, or research institution. Classification must be based on the characteristics of the material and the available information concerning the presence and risk of pathogens.
If an infectious substance meets the criteria for Category A, it must instead be classified as UN 2814 – Infectious substance, affecting humans, or UN 2900 – Infectious substance, affecting animals only, as applicable.
Likewise, a human or animal specimen for which there is minimal likelihood that pathogens are present may qualify as an Exempt Human Specimen or Exempt Animal Specimen, subject to the applicable requirements discussed below.
Packaging UN 3373 for Air Transportation
For air transportation, UN 3373 shipments are prepared according to the applicable requirements of Packing Instruction 650 (PI 650).
The packaging system is based on multiple layers of containment and generally includes:
- a primary receptacle containing the specimen;
- a secondary packaging surrounding the primary receptacle; and
- an outer packaging of adequate strength for its intended use.
For liquid specimens, sufficient absorbent material must be placed between the primary receptacle and secondary packaging to absorb the contents in the event of leakage. When multiple fragile primary receptacles are packed together, they must also be wrapped or separated as necessary to prevent contact and damage during transportation.
The completed package must meet the applicable PI 650 performance and construction requirements and display the required UN 3373 mark together with the proper shipping name Biological Substance, Category B.
These requirements are intended to provide multiple levels of containment so that a failure of the primary receptacle does not result in release from the package during normal conditions of transportation.
UN 3373 Is Regulated, but It Does Not Require a Shipper’s Declaration
One of the most important distinctions between Category A and Category B concerns dangerous goods documentation. When a UN 3373 shipment is prepared in accordance with the applicable Category B provisions, a Shipper’s Declaration for Dangerous Goods is not required. This should not be interpreted to mean that UN 3373 is unregulated.
The shipper must still comply with the applicable classification, packaging, marking, documentation, quantity, and transportation requirements. Under IATA PI 650, if an air waybill is used, the Nature and Quantity of Goods box must show UN 3373, Biological Substance, Category B, and the number of packages unless these are the only packages in the consignment.
If dry ice is used to maintain the required temperature, it introduces separate requirements because UN 1845 – Carbon dioxide, solid (Dry ice) is itself regulated for air transportation. The use of dry ice as a refrigerant does not change the specimen’s classification from UN 3373, nor does it by itself require a Shipper’s Declaration when the applicable dry-ice provisions are satisfied.
The distinction between the biological substance and the refrigerant is discussed in greater detail later in this article.
Exempt Human and Animal Specimens
Not every human or animal specimen containing biological material is regulated as an infectious substance. A patient specimen for which there is minimal likelihood that pathogens are present may qualify as an Exempt Human Specimen or Exempt Animal Specimen, as applicable.
This determination requires professional judgment based on factors such as the known medical history, symptoms, individual circumstances of the source, and local endemic conditions.
The word “exempt” should therefore not be interpreted as meaning that any research specimen or any specimen believed to be harmless can automatically be shipped under an exemption.
Examples may include certain specimens collected for monitoring cholesterol, blood glucose, hormone levels, or organ function; specimens collected for therapeutic drug monitoring; certain insurance or employment testing specimens; pregnancy tests; biopsies used to detect cancer; and antibody testing performed in the absence of concern for infection.
These examples do not automatically qualify for exemption. The determination still depends on the circumstances of the specimen and professional judgment regarding the likelihood that pathogens are present. For example, a description such as “Exempt Animal Specimen – Mouse Brain Tumor Tissue Samples” may be appropriate when the material actually satisfies the applicable criteria for an exempt animal specimen.
Packaging Exempt Human and Animal Specimens
“Exempt” does not mean that the specimen can be shipped without appropriate containment. For air transportation, packaging for exempt human or animal specimens should provide multiple levels of protection against leakage or damage during normal transportation conditions.
The packaging should generally consist of:
- a leak-proof primary receptacle;
- a leak-proof secondary packaging; and
- an outer packaging of adequate strength for its capacity, mass, and intended use.
For liquids, sufficient absorbent material should be placed between the primary receptacle and secondary packaging to absorb the entire contents in the event of leakage. When multiple fragile primary receptacles are placed within the same secondary packaging, they should be individually wrapped or otherwise separated to prevent contact between them.
The outer package must be marked “Exempt human specimen” or “Exempt animal specimen”, as appropriate. The scientific description and transportation classification should reflect what the material actually is.
Not Every Non-Infectious Biological Material Is an “Exempt Specimen”
There is another distinction that is easy to overlook. A biological material that is not regulated as an infectious substance does not necessarily need to be described as an Exempt Human Specimen or Exempt Animal Specimen.
Some biological materials may simply fall outside Division 6.2 because they are not known or reasonably expected to contain infectious substances and do not meet another applicable hazardous-material classification. Examples may include certain purified materials, fixed tissues, non-infectious cell preparations, DNA or RNA preparations, or other research materials.
Other materials may also fall outside the infectious-substance regulations when any pathogens originally present have been neutralized or inactivated so that they no longer pose a health risk, provided the material does not meet the criteria for another hazard class.
Certain environmental samples, including some food and water samples that are not considered to pose a significant risk of infection, may similarly fall outside Division 6.2 requirements. The specific characteristics of the material must still be evaluated.
In addition, being non-regulated for dangerous goods transportation does not necessarily mean that the material is free from customs, import, export, permit, or other government requirements. Transportation classification and import admissibility are separate determinations.
Classification and Temperature Control Are Separate Questions
This distinction is particularly important in biological logistics. The classification of the biological material answers one question: What transportation regulations apply to the material itself?
Temperature control answers another: What conditions must be maintained to preserve the material during transportation? A shipment may therefore contain an Exempt Animal Specimen and still require dry ice.
Likewise, a UN 3373 Category B shipment may be packed with dry ice. The classification of the specimen does not change simply because dry ice is used as a refrigerant. However, dry ice introduces its own transportation requirements.
Dry Ice as a Refrigerant: A Critical Documentation Distinction
Dry ice is UN 1845 – Carbon dioxide, solid, Class 9, and is regulated as a dangerous good for air transportation. But when dry ice is used to maintain the required temperature of biological samples, it is functioning as a refrigerant, not as the product being transported or traded. That distinction matters when preparing shipment documentation.
A commercial invoice or packing list describes the goods involved in the commercial or customs transaction. Dry ice used solely as packaging coolant would not ordinarily be presented as though it were an additional product or commodity being sold.
For example, commercial or packing documentation may state that the shipment is packed with 15 kg of dry ice when that information is operationally useful. This does not make the dry ice a separate transactional product.
Dangerous goods transportation documentation follows a different set of rules. For air transportation, when dry ice is used as a refrigerant and a Shipper’s Declaration is not otherwise required, the applicable transport documentation must identify the dry ice in the prescribed manner, including UN 1845 – Carbon dioxide, solid (Dry ice) together with the required package and net-quantity information. The package itself must also carry the applicable dry-ice marks and Class 9 label.
Therefore, the fact that dry ice is not a separate line item on the commercial invoice does not mean that its presence is omitted from air-transport documentation. The distinction is between commercial declaration and dangerous-goods hazard communication.
Does Dry Ice Require a Shipper’s Declaration?
When dry ice is used as a refrigerant under the applicable air-transport provisions, a Shipper’s Declaration for Dangerous Goods is generally not required solely because the shipment contains dry ice.
Instead, the prescribed dry-ice information is provided on the air waybill or other permitted transport documentation, and the package is marked and labeled accordingly. The underlying biological material can change the documentation requirements.
Exempt Specimen + Dry Ice
The specimen may be exempt from Division 6.2 requirements, while the dry ice remains subject to its applicable air-transport requirements. A Shipper’s Declaration is not required solely for the dry ice when the applicable exception is satisfied.
UN 3373 Category B + Dry Ice
UN 3373 does not require a Shipper’s Declaration when prepared under the applicable Category B provisions, and dry ice used as a refrigerant can also be transported without a Shipper’s Declaration when the applicable requirements are satisfied.
However, both the biological substance and dry ice must still be properly communicated through the required package markings, labels, and transportation documentation.
UN 2814 or UN 2900 Category A + Dry Ice
This is different. Category A infectious substances require the applicable dangerous goods documentation. When dry ice is included as a refrigerant, its presence must also be reflected in accordance with the applicable dangerous goods documentation requirements.
The absence of a separate commercial line item for dry ice therefore should never be confused with an absence of dangerous goods transportation requirements.
Why Correct Classification Matters
Incorrect classification can create problems long before a shipment reaches customs. A shipment may be:
- rejected during airline acceptance;
- returned for repackaging;
- held while markings or labels are corrected;
- delayed while documentation is amended;
- routed differently because of dangerous goods restrictions; or
- prevented from moving until appropriately trained personnel prepare the shipment.
For temperature-sensitive materials, these delays introduce another risk. Every hour spent correcting a shipment after it has been packed can consume part of the packaging system’s available thermal duration.
Correct classification is therefore not simply a regulatory exercise. It is part of protecting the shipment.
Who Is Responsible for Classification?
The shipper bears responsibility for properly classifying and describing hazardous materials offered for transportation. This is particularly important for biological materials because a logistics provider may not possess the scientific or medical information necessary to independently determine whether a pathogen is present or what hazard the material represents.
Laboratories, researchers, manufacturers, clinical organizations, and other shippers should therefore provide sufficient information for the material to be properly evaluated.
A specialized logistics provider like Kolob Express can assist with transportation requirements, packaging, documentation, routing, and regulatory coordination, but accurate classification begins with accurate information about the material itself.
Classification Comes Before Transportation
A biological shipment should not begin with the question “Which airline can move this package”. It should begin with “What exactly are we shipping”.
From that answer follow the classification, packaging, temperature-control strategy, marks and labels, documentation requirements, carrier acceptance requirements, and ultimately the transportation plan.
Whether a material is Category A, Category B, an exempt specimen, or outside the infectious-substance classification entirely can fundamentally change how the shipment must be prepared. Determining that classification before the shipment moves reduces avoidable delays and helps protect both regulatory compliance and the integrity of the material.
Planning a Biological Shipment?
Kolob Express provides specialized logistics support for Life Sciences & Healthcare shipments, including biological and research materials requiring precise transportation, temperature control, documentation, and regulatory coordination.
Our capabilities include temperature-controlled transportation, validated packaging solutions, dry ice replenishment, data loggers, airfreight, customs clearance, shipping documentation advisement, pickup and delivery, and government-compliance-driven logistics.
Requirements vary according to the material, classification, origin, destination, intended use, temperature requirements, and applicable regulations.
For a broader overview of the planning process, see our pillar article “Shipping Biological Samples Internationally: What You Need to Know Before the Shipment Moves”.
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This article provides general logistics information and is not legal, medical, scientific, or regulatory advice. Classification and transportation requirements should be determined using the current applicable regulations and information specific to the material being shipped.
Key regulatory points were checked against IATA Dangerous Goods Regulations, Packing Instruction 650 (67th Edition, 2026), and U.S. DOT/PHMSA infectious-substance guidance. Always verify current regulations and carrier variations before applying this article operationally.