Pet Clinic Sample Shipping: Specimen Bag Seals and UN3373 Rules

Quick Summary: Veterinary clinics in Canada ship blood, urine, biopsy and swab samples to diagnostic labs every day, and the bags those samples travel in must do two jobs at once: contain the specimen without leaking, and satisfy transport regulations for biological substances. For most routine veterinary samples, a 95kPa-rated leak-proof specimen bag with a tamper-evident seal is the practical standard; for samples that qualify as infectious substances, UN3373 Category B packaging rules apply. This article maps the bag requirements to the common veterinary sample types and explains what the seal ratings actually mean.

A veterinary clinic in Calgary asked us a question that comes up after every courier pickup: "Our lab form says Category B, UN3373, but we just put the blood tubes in a zip bag and hand it to the courier. Is that right?" The short answer is that routine veterinary samples usually travel as Biological Substance Category B, and Category B has packaging rules — including a leak-proof primary container, absorbent material, and a rigid or flexible outer packaging that meets the 95kPa pressure test. The specimen bag is part of that system, and choosing the wrong one can mean a returned sample, a biohazard exposure, or a compliance finding. This article walks through the specimen bag requirements for Canadian veterinary clinics by sample type, so the right bag is on the shelf before the next pickup.

Why Specimen Bag Standards Matter in Veterinary Medicine

Veterinary samples are biological material, and in Canada the transport of biological substances is regulated under the Transportation of Dangerous Goods (TDG) framework, which aligns with the UN Model Regulations used internationally. Most routine diagnostic specimens — blood, serum, urine, faeces, swabs — are classified as Biological Substance Category B (UN3373) when they are known or reasonably expected to contain a pathogen that does not meet the definition of a Category A infectious substance. Category B is the default for routine veterinary diagnostics, and it carries specific packaging requirements (TDG Regulations, referenced by name; PHAC laboratory biosafety guidance, PHAC Laboratory Biosafety and Biosecurity).

The specimen bag is the outermost layer of the triple packaging system for Category B: a leak-proof primary container (the tube or vial), a leak-proof secondary packaging with absorbent material, and an outer packaging that protects the contents. A 95kPa-rated specimen bag serves as that outer packaging for many veterinary samples — but only if it is certified to withstand the pressure test and sealed correctly. The 95kPa rating refers to an internal pressure test that confirms the bag can hold its seal under the pressure conditions specified in the transport regulations (IATA DGR and the UN Model Regulations, IATA Dangerous Goods Regulations).

What the 95kPa Seal Rating Actually Means

The 95kPa rating is not a marketing claim — it is a test result. The test is based on the international standard for packaging for transport of infectious substances, which requires the outer packaging to withstand an internal pressure differential of 95 kPa (about 13.8 psi) without leakage. For a specimen bag, that means the seal and film must hold under the pressure conditions that can occur during transport, including altitude changes in air cargo.

For buyers, the practical checks are simple:

• Look for the rating on the packaging. A compliant bag states its 95kPa certification or the applicable transport standard on the box or spec sheet.
• Check the seal type. Tamper-evident seals (adhesive closures that show evidence of opening) are preferred for chain-of-custody samples; zip closure closures are convenient but should be confirmed as leak-proof for the intended use.
• Confirm the size fits the lab's requirement. Veterinary labs often specify bag dimensions on their requisition forms — a 6x9-inch bag is a common standard for blood tubes and small vials.
• Use the pouch-and-paper format where required. Many Canadian diagnostic labs use specimen bags with a separate document pouch so the requisition travels with the sample without touching the specimen container.

Matching Specimen Bags to Veterinary Sample Types

Not every veterinary sample needs the same bag. The table below maps common sample types to the recommended packaging approach, based on the triple packaging system and practical lab requirements.

For samples that are not infectious — such as routine wellness panels where the risk assessment indicates no known pathogen — a standard leak-proof specimen bag with proper labelling is generally sufficient. The distinction matters because it affects both cost and compliance: a clinic does not need Category B packaging for every tube, but it does need Category B packaging for samples that fall under the UN3373 classification. When in doubt, follow the lab's requisition instructions and the clinic's risk assessment; the default for diagnostic samples is Category B.

UN3373 and Category B: When the Rules Apply

The UN3373 classification applies to Biological Substance Category B: infectious substances that do not meet the criteria for Category A. For veterinary clinics, this covers most diagnostic samples where an infectious agent could be present — blood from a febrile animal, swabs from a suspected infection, faeces from a diarrhoea case. The packaging requirements under TDG and the UN Model Regulations for Category B are:

• Primary container(s) that are leak-proof and contain the sample;
• Secondary packaging that is leak-proof and contains absorbent material sufficient to absorb the entire contents;
• Outer packaging (which can be the specimen bag for small samples) that is marked with the UN3373 diamond label and is strong enough for the transport mode;
• Documentation and labelling per the courier's and regulator's requirements.

Note that the 95kPa test applies to the outer packaging of the triple packaging system. A specimen bag that carries a 95kPa certification can serve as the outer packaging for Category B samples when the primary and secondary containers are properly prepared. If the clinic uses a rigid box or cooler instead, that outer packaging must also meet the applicable pressure and strength requirements (IATA DGR, IATA Dangerous Goods Regulations; PHAC biosafety guidance).

Labelling and Documentation for Veterinary Samples

Beyond the bag itself, Canadian veterinary clinics must label sample shipments correctly. For Category B (UN3373) shipments, the outer packaging carries the UN3373 diamond label with "Biological Substance, Category B" on a contrasting background. The shipper's and receiver's information goes on the outside, and the requisition or manifest accompanies the shipment in the bag's document pouch or in a separate envelope.

Provincial laboratory licensing rules and the diagnostic labs themselves often add requirements: some labs specify their own bag, some require the requisition in the pouch, and some restrict courier services to approved handlers. The clinic's lab manual is the authoritative source for the receiving lab's packaging expectations, and the TDG Regulations define the minimum transport requirements. Using a 95kPa bag with a document pouch covers both: it meets the transport standard and carries the paperwork in the right place.

Common Veterinary Specimen Bag Mistakes

The most common packaging errors in veterinary sample shipping are practical, not exotic:

• Reusing bags. Specimen bags are single-use. A bag that has carried one sample has lost its seal integrity and its sterility for chain-of-custody purposes.
• Overfilling. A bag stuffed with tubes and vials cannot seal correctly. The 95kPa rating assumes the bag is closed with room for the contents, not stretched.
• Skipping absorbent material. Category B secondary packaging requires absorbent material capable of absorbing the full contents. A small absorbent pad may not cover a tube leak in a large bag.
• Mixing samples without segregation. Different sample types in one bag increase the contamination and confusion risk; most labs prefer one bag per patient or per requisition.
• Ignoring the lab's bag requirement. Some labs return samples packaged in non-approved bags, or reject the requisition. Check the lab manual.

Building a Specimen Bag Inventory for Your Clinic

Veterinary clinics should carry more than one specimen bag SKU. A practical inventory:

• 6x9-inch 95kPa bags with document pouch — the workhorse for blood tubes, urine cups and swabs (most common lab requirement);
• Larger bags (8x10 or 10x13 inch) — for biopsy jars, formalin containers and multi-sample requisitions;
• Standard leak-proof zip bags — for non-infectious samples and internal transport within the clinic;
• Absorbent wipes or pads — for the secondary packaging requirement on Category B shipments;
• UN3373 diamond labels and shipping forms — for courier packaging when the clinic prepares shipments.

CliniEco Medical carries a 6x9-inch 95kPa certified specimen bag in a 100-pack with a document pouch, designed for the blood/urine/swab samples that make up most veterinary diagnostic shipments. For clinics that want to align their full diagnostic supply chain, the same order can include nitrile exam gloves for sample collection and disinfectant wipes and surface cleaners for bench and transport-surface cleaning.

Frequently Asked Questions

Are veterinary specimens shipped under UN3373?

Most routine veterinary diagnostic samples — blood, urine, swabs, faeces — are classified as Biological Substance Category B (UN3373) when they may contain a pathogen that does not meet Category A criteria. Category B packaging rules apply, including a leak-proof primary container, absorbent material, and a compliant outer packaging such as a 95kPa-certified specimen bag.

What does 95kPa mean on a specimen bag?

It means the bag passed an internal pressure test of 95 kPa (about 13.8 psi) without leaking — the standard used for packaging that transports infectious substances. For buyers, it is the indicator that the bag meets the pressure/leak requirement for Category B shipments and general specimen transport.

Can I use a regular zip closure bag for blood samples?

For Category B shipments, no. The transport regulations require the outer packaging to meet the applicable pressure and strength requirements, and a regular zip bag does not carry that certification. Use a 95kPa-certified specimen bag for diagnostic samples, and keep regular zip bags for non-infectious internal transport.

What size specimen bag do veterinary clinics need?

Most Canadian veterinary labs accept a 6x9-inch 95kPa bag with a document pouch for blood tubes, urine cups and swabs. Larger sizes (8x10 or 10x13 inch) are useful for biopsy jars and multi-sample requisitions. Check your lab's requisition form for its preferred size.

Is absorbent material required in a specimen bag?

For Category B shipments, yes. The secondary packaging must contain absorbent material sufficient to absorb the entire contents of the primary container in case of leakage. Many specimen bag systems include an absorbent pad or wipe for this purpose.

Can specimen bags be reused?

No. Specimen bags are single-use. Reusing a bag compromises seal integrity, increases contamination risk, and breaks chain-of-custody for samples that require it. Discard the bag after each shipment.

Do I need a UN3373 label on every veterinary specimen bag?

The UN3373 diamond label goes on the outer packaging of Category B shipments. If the 95kPa specimen bag serves as the outer packaging, it (or the outer wrapper) carries the label and the shipper/receiver information. Non-infectious samples do not require the label.

Where can Canadian veterinary clinics buy certified specimen bags?

CliniEco Medical carries 6x9-inch 95kPa certified specimen bags with document pouches in 100-packs, with wholesale pricing available for volume orders. Bulk inquiries qualify for the wholesale tier with a $300 minimum order.

References

1. PHAC — Laboratory Biosafety and Biosecurity (transport and packaging guidance context): PHAC Laboratory Biosafety
2. IATA — Dangerous Goods Regulations (Category B / UN3373 packaging requirements): IATA DGR
3. Transportation of Dangerous Goods Regulations (TDG, SOR/2001-286) — referenced by name for the Canadian regulatory framework for transporting biological substances.
4. Health Canada — Medical devices regulatory framework: Health Canada Medical Devices
5. PHAC — Routine Practices and Additional Precautions: PHAC Routine Practices
6. CDC — Guideline for Isolation Precautions (infection prevention context): CDC isolation precautions
7. World Health Organization — Infection prevention and control resources: WHO IPC
8. Journal of Hospital Infection (Elsevier) — Infection control research: JHI journal
9. Antimicrobial Resistance & Infection Control (Springer) — Open-access IPC research: ARIC journal
10. American Journal of Infection Control (Elsevier) — Infection control research: AJIC journal

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