Biohazard shipping containers: how a swab travels safely
Most hereditary-cancer specimens — saliva, buccal swabs, EDTA whole blood — ship as UN3373 "Biological substance, Category B" under IATA Packing Instruction P650. This explainer walks the triple-packaging system, the labels, and where Category A differs. Educational only — your lab's courier and dangerous-goods team set the binding rules.
Why a saliva tube counts as dangerous goods
A buccal cell or saliva sample carries no acute hazard, yet transport regulators still classify human diagnostic specimens as Class 6.2 infectious substances unless they are known to be non-infectious. The default category for routine clinical and research samples — including hereditary-cancer panels run on BRCA1, BRCA2, PALB2 and the wider gene set — is Category B, proper shipping name Biological substance, Category B, identifier UN3373. The far stricter Category A (UN2814 for human pathogens, UN2900 for animal) is reserved for cultures and substances capable of causing permanent disability or fatal disease in otherwise-healthy people. A genomic DNA extraction or a stabilised saliva tube is not that — but it still ships in a compliant container.
The governing rule for air is IATA Packing Instruction P650; the equivalent road rule (ADR) is also numbered P650 and is largely harmonised, with minor differences.
The triple-packaging system, layer by layer
P650 (Category B) and P620 (Category A) share the same three-layer logic. The container fails if any layer is missing.
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1 · Primary receptacle
The leak-proof, sift-proof tube or vial that actually holds the specimen — a stabilised-saliva tube such as an
OG-500, a buccal-swab transport tube, or an EDTA blood vacutainer. For liquids it is sealed (heat-seal, skirted cap, or taped screw cap). - 02
2 · Absorbent material
For any liquid, enough absorbent (gauze, cellulose wadding) sits between primary and secondary to soak up the entire contents if the primary breaks. Skip this and the package is non-compliant even if nothing leaks in transit.
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3 · Secondary packaging
A second leak-proof container — a sealed biohazard zip bag or rigid canister — enclosing one or more primaries. For liquids, either the primary or this secondary must withstand 95 kPa internal pressure without leaking (the air-pressure differential test).
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4 · Itemised list
For Category B the contents list (the requisition / manifest) is placed between the secondary and the outer packaging, identifying the specimen.
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5 · Rigid outer packaging
A strong outer box. For Category B it need not be UN-certified, but the completed package must pass a 1.2 m drop test and present at least one face of 100 × 100 mm to carry the mark. Category A demands a fully UN-certified outer.
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6 · Mark & label
The outer shows the
UN3373diamond mark (side ≥ 50 mm) with "Biological substance, Category B" beside it, plus sender and receiver. Liquids over the carrier's threshold may also need orientation (up) arrows.
Category A vs Category B at a glance
The single most consequential decision is which category your specimen falls into — it changes the packing instruction, the outer-packaging certification, and the quantity limits.
| Attribute | Category A | Category B (routine diagnostics) |
|---|---|---|
| UN number | UN2814 (human), UN2900 (animal) | UN3373 |
| Proper shipping name | Infectious substance, affecting humans / animals | Biological substance, Category B |
| Packing instruction | P620 | P650 |
| Typical contents | Cultures of high-risk pathogens; permanent-disability / fatal risk | Saliva, buccal swab, blood, DNA extract for diagnosis |
| Outer packaging | UN-certified, performance-tested | Strong outer; not UN-certified, but 1.2 m drop test |
| Liquid limit per package | 50 mL/g passenger aircraft; 4 L/kg cargo aircraft | Primary ≤ 1 L; complete package ≤ 4 L |
| Solid limit | 4 kg cargo aircraft | ≤ 4 kg |
| Hazard label | Class 6.2 infectious-substance diamond | UN3373 mark + text (no Class 6.2 diamond) |
Table 1. Comparison of Class 6.2 infectious-substance shipping categories (IATA DGR). Figures reflect P650 / P620 air-transport limits and are indicative; confirm with your dangerous-goods adviser.
Category B (UN3373 / P650) air-transport quantity limits
Under P650, per-package limits keep a single failure small. Whichever is reached first governs.
Single tube/vial ceiling
Sum across all primaries
Glossary
The terms a courier label and a dangerous-goods checklist will use.
- UN3373
- The four-digit UN identifier and mark for "Biological substance, Category B" — the class of most diagnostic specimens, shipped under P650.
- P650
- IATA/ADR Packing Instruction governing Category B: triple packaging, absorbent for liquids, 95 kPa, 1.2 m drop, ≥ 100 × 100 mm outer face.
- P620
- The stricter packing instruction for Category A (
UN2814/UN2900), requiring UN-certified, performance-tested outer packaging. - Triple packaging
- Primary receptacle + secondary packaging + rigid outer, with absorbent between the first two for liquids — the shared backbone of both P620 and P650.
- 95 kPa rule
- For liquid Category B, the primary or secondary must hold 95 kPa internal pressure without leak, simulating an air-pressure differential.
- Class 6.2
- The dangerous-goods division for infectious substances. Category A carries the 6.2 diamond label; Category B (UN3373) uses its own mark instead.
Common questions
Does a saliva DNA kit really need biohazard packaging?
Almost always shipped as UN3373, Category B, under P650. Even stabilised saliva that is non-infectious in practice is treated as a diagnostic specimen unless formally exempted. Some stabilised, room-temperature kits ship under courier-specific exemptions, but the triple-packaging logic still applies. Follow the instructions in your kit and your lab's courier account.
What is the difference between Category A and Category B again?
Category A (UN2814/UN2900, P620) covers substances that can cause permanent disability or death in healthy people — cultures of high-risk pathogens. Category B (UN3373, P650) is everything else routine: blood, saliva, swabs, extracted DNA for hereditary-cancer panels. Category A needs UN-certified outers; Category B does not, though it must still survive a 1.2 m drop.
Why absorbent material if my sample is solid?
Absorbent is required only when a liquid is present, sized to soak up the entire primary contents. A dry buccal swab or a lyophilised extract does not need it — but a saliva or blood tube does, every time.
What does the 95 kPa requirement protect against?
Cargo holds depressurise at altitude. For liquid Category B, the primary or secondary receptacle must hold a 95 kPa internal pressure differential without leaking, so a sealed tube does not vent or burst in flight.
Is this medical advice?
No. This page explains transport classification for general understanding. It does not replace your laboratory's dangerous-goods procedures or carrier rules, and it is not clinical advice — for any decision about testing, speak with a clinician or genetic counsellor.
- [1]IATA DGR / P650. International Air Transport Association. Dangerous Goods Regulations — Packing Instruction 650, Biological substance, Category B (UN3373): triple packaging, 95 kPa, 1.2 m drop test, ≥ 100 × 100 mm outer surface.↗
- [2]IATA DGR / P620. International Air Transport Association. Packing Instruction 620, Category A infectious substances (UN2814 / UN2900): UN-certified performance-tested packaging; 50 mL/g passenger and 4 L/kg cargo aircraft limits.↗
- [3]Air Sea Containers — P650. Packing Instruction P650 for UN3373: primary ≤ 1 L for liquids, complete package ≤ 4 L; solids ≤ 4 kg; absorbent and 95 kPa requirements.↗
- [4]ShipMercury — IATA Biological Packaging Guide. Differences between UN2814, UN2900 and UN3373 and the PI620 / PI650 packing instructions.↗
- [5]Intelsius — UN3373 & P650 Compliance. Triple-packaging requirements, performance criteria and labelling for UN3373 Category B shipments.↗
A specimen is only as good as its journey
Packaging protects the sequence. See how collection method, stabilisation buffer and cold-chain handling shape what reaches the lab.