What 172.331(c) means in plain language
When you transport hazmat in bulk form—liquids, gases, or solids in large quantities—federal rules require each package to display proper identification numbers. These ID numbers (also called UN numbers or proper shipping names) tell emergency responders, inspectors, and other handlers exactly what material is in the container and how to handle it safely.
A 172.331(c) citation means an inspector found bulk hazmat packages on your vehicle that lacked these required identification markings or had incomplete/incorrect markings. This isn't a paperwork technicality. The ID number is the primary way the system communicates hazard information when something goes wrong—a leak, accident, or emergency.
Common scenarios include missing placard information on drums, tankers without proper stenciling, or totes lacking required labeling. The violation itself does not automatically trigger an out-of-service order, but improper hazmat identification is treated seriously because it directly impacts public safety.
What our enforcement data actually shows
Across our 13 million+ roadside inspection records, 172.331(c) has been cited 13 times all-time. In the last 12 months, we recorded zero citations for this code, and zero citations in the last 90 days. This makes 172.331(c) a relatively uncommon violation, ranking #2110 out of 3,036 FMCSR codes by citation volume.
When inspectors do cite this code, the out-of-service rate stands at 30.8%—meaning roughly 3 out of 10 vehicles were placed out of service. This rate is nearly identical to the all-FMCSR average of 31.4%, indicating that enforcement severity for this code aligns with typical hazmat-related violations. Of the 13 all-time citations, 4 resulted in out-of-service placement and 9 did not.
The rarity of recent citations suggests either strong compliance in the industry or that inspectors catch hazmat ID issues through related violations (like general placarding violations) before they document this specific code.
Who gets cited most
Our inspection records show no single carrier dominates citations for 172.331(c). The data indicates fleets such as E F CORPORATION, USA TRUCK LLC, LOTT OIL CO INC, TRANSPORT SYLVESTER & FORGET INC, and JRP WASTE OIL SERVICE INC each received one citation. No geographic concentration or carrier-specific pattern emerges from the 13 all-time citations.
Vehicle makes most frequently cited include Freightliner (FRHT) with 3 citations, followed by Volvo (VOLV) and Godaddy-branded vehicles (GDAN) with 2 citations each. The remaining citations were spread across single vehicles of other makes. This distribution reflects the general prevalence of these truck models in the fleet population rather than a systemic issue with any particular manufacturer.
How severe is this compared to similar codes
Hazmat identification and labeling violations fall into a spectrum. Our database shows that general loading/unloading hazmat violations (177.834A-HMC and 177.834(a)) are far more frequently cited—3,954 and 3,839 times respectively—and carry dramatically higher out-of-service rates of 99.2% and 97.9%. These codes trigger nearly certain removal from service because they typically involve active handling of hazardous materials without proper controls.
Placarding violations in general (177.817(a)) appear 2,274 times in our records with a 75.1% out-of-service rate, significantly higher than 172.331(c)'s 30.8%. By contrast, placard deterioration (177.817(e)) is cited 2,038 times but has only a 5.2% out-of-service rate, suggesting that cosmetic or minor marking issues are treated leniently. The data indicates that 172.331(c)—missing ID numbers entirely—falls between cosmetic defects and active loading violations in severity.
How to avoid it
Prevention is straightforward and starts before you accept the load:
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Verify all bulk containers before departure. Walk around drums, tankers, and totes with a checklist. Confirm each item displays its proper shipping name or UN identification number clearly and legibly. Don't assume the shipper got it right.
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Request documentation from the shipper. The Bill of Lading and shipping papers must match the physical containers. Cross-reference the material description, proper shipping name, and hazard class against what's marked on the package. Discrepancies are red flags.
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Inspect markings for legibility, not just presence. Faded, smudged, or partially obscured ID numbers fail the requirement. If you can't read it clearly in daylight, neither can an inspector. Request fresh markings before loading.
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Know the material you're hauling. Familiarize yourself with the hazard class, UN number, and required placards for your load. This knowledge helps you spot missing or incorrect markings and gives you confidence during inspection.
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Document the condition at pickup. Take photos of marked containers before departure. If an inspector later finds missing ID numbers, you have evidence of the condition when you accepted the load—important for liability and dispute resolution.
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Maintain your vehicle's placards and markings too. Your vehicle's external placards must also display proper ID information. Dirt, damage, or fading renders them ineffective. Clean them regularly and report damage to your carrier immediately.
The 13 all-time citations for this code and zero citations in the last 90 days suggest that most carriers are handling bulk hazmat ID requirements correctly. Stay on the right side of that trend by treating container markings as non-negotiable before you roll.