Triple packaging

Marking the outer

On this page11

What goes on the outside Which is why one surface must be 100 mm by 100 mm So a small parcel is not a cheaper parcel Nothing we sell should be marked The sample still needs identifying And it has to survive a cold bag Label the container, not the cap An itemised list travels inside Responsible person details go on the outer too Which is the division this property keeps making References

UN3373 belongs to the outer packaging. Nothing on this shelf should carry it.

What goes on the outside

The proper shipping name, "Biological substance, Category B", and the identification number UN3373. Both belong to the rigid outer packaging.

Which is why one surface must be 100 mm by 100 mm

"At least one surface of the outer packaging must have a minimum dimension of 100 mm by 100 mm (3.9 inches)." The dimension exists so the mark has somewhere to go and stays legible.

So a small parcel is not a cheaper parcel

Shipping one tube does not let you shrink the box below that dimension. The mark has to fit, which sets a floor on the outer regardless of what is inside it.

Nothing we sell should be marked

A primary receptacle carrying a UN3373 mark is a container misrepresenting what it is. The mark describes a tested assembly and a bottle is not one.

The sample still needs identifying

Which is a different label doing a different job: patient or site, date, time of collection, and whatever the laboratory asks for. That one belongs on the primary receptacle.

And it has to survive a cold bag

Everything in a transport bag is damp. A paper label on a tube in a cooler lifts, and an unidentified specimen is a discarded specimen.

Label the container, not the cap

Caps get swapped during collection and at the bench. The identity belongs on the thing holding the sample, which is the same conclusion the field sampling property reaches from the other direction.

An itemised list travels inside

Between the secondary and the outer, so somebody opening a damaged parcel knows what they are looking at before they find out the hard way.

Responsible person details go on the outer too

Somebody contactable who knows what is in the parcel. A process requirement rather than a packaging one, and part of the same system.

Which is the division this property keeps making

The outer carries the regulatory identity. The primary carries the sample's identity. We supply the second and not the first.

References

49 CFR 173.199, Category B infectious substances. "A Category B infectious substance must be packaged in a triple packaging consisting of a primary receptacle, a secondary packaging, and a rigid outer packaging." Absorbent material "must be placed between the primary receptacle and secondary packaging" and "must be of sufficient quantity to absorb the entire contents of the primary receptacles". "The primary receptacle or the secondary packaging must be capable of withstanding without leakage an internal pressure producing a pressure differential of not less than 95 kPa." "The packaging must be capable of successfully passing the drop test in 178.609(d) of this subchapter at a drop height of at least 1.2 meters (3.9 feet)." "At least one surface of the outer packaging must have a minimum dimension of 100 mm by 100 mm (3.9 inches)." By aircraft, each primary receptacle may not exceed 1 L and each outer packaging 4 L for liquids, or 4 kg for solids. law.cornell.edu

49 CFR 173.134(a)(1)(ii) defines Category B as "an infectious substance that is not in a form generally capable of causing permanent disability or life-threatening or fatal disease in otherwise healthy humans or animals when exposure to it occurs", to be described as "Biological substance, Category B" and assigned identification number UN3373. Paragraph (b)(11) excepts human or animal samples transported for routine testing unrelated to the diagnosis of infectious disease where there is a low probability the sample is infectious. law.cornell.edu

Written from 49 CFR 173.199 and 173.134, and from the catalog as it stood on 19 October 2026. Nothing here is offered as a compliant primary receptacle for a regulated shipment: the pressure and drop requirements attach to a tested assembly, not to a bottle. Category A infectious substances are a different packaging instruction entirely and are not summarized. Sterility is not claimed for any product, and what a laboratory will accept is the laboratory's to say.