What 172.331-HMM means in plain language
This citation addresses a specific hazardous materials marking requirement: bulk packages carrying hazmat must display proper ID numbers in the locations and manner required by federal regulation. When an inspector finds a bulk package without the required ID number affixed, or with an ID number that's missing, illegible, or improperly positioned, the violation is recorded as 172.331-HMM.
The requirement exists so emergency responders, handlers, and enforcement personnel can quickly identify what's in the container and respond appropriately if something goes wrong. A missing or obscured ID number defeats that purpose and creates a compliance gap, even if the hazmat itself is properly loaded and the vehicle is mechanically sound.
This is a marking-specific violation, separate from broader placarding or labeling failures. It's narrowly focused on one element: the affixed identification number on the package itself.
What our enforcement data actually shows
Across our 13 million+ inspection records, this code has never resulted in an out-of-service citation. Our data shows an out-of-service rate of 0.0% for 172.331-HMM—compared to the all-FMCSR average of 31.4%, this violation is treated as non-critical for immediate vehicle removal.
Enforcement volume is extremely low. We've recorded 5 citations all-time, 3 in the last 12 months, and 1 in the last 90 days. In the most recent monthly snapshot (June 2025, July 2025, and March 2026), this code appears once per month or less. Nationally, 172.331-HMM ranks #2406 out of 3,036 FMCSR codes by citation frequency—it's rarely cited.
The rarity of enforcement does not mean the requirement is unimportant. It may reflect that most carriers handle this marking step correctly, or that roadside inspectors encounter it less frequently than other hazmat violations.
Who gets cited most
Our inspection records show this violation is geographically sparse. In the last 180 days, Colorado accounts for 1 citation with a 0.0% out-of-service rate.
All-time, we see citations distributed across five different carriers, each with a single citation: STRANCO LLC, RUMMEL'S OILFIELD SERVICES INC, J PARKER FARMS LLC, DURRANI INVESTMENTS CORP, and RIVERBEND TRANSPORTATION LLC. No carrier pattern emerges from this data; the violations are scattered. Vehicle makes cited include Freightliner and Wabash National (each with 2 citations) and Ford, Peterbilt, and others (1 citation each).
The low citation count across all carriers and states suggests this is not a systemic enforcement area, but rather a sporadic finding when inspectors specifically examine bulk hazmat package markings.
How severe is this compared to similar codes
Within the hazardous materials category, enforcement patterns vary dramatically. Placarding and loading/unloading violations dominate the citation landscape and carry far higher out-of-service rates.
For example, 177.834A-HMC (general loading/unloading hazmat) has 3,954 citations with a 99.2% out-of-service rate. 177.817(a) (placarding violation) shows 2,274 citations with a 75.1% OOS rate. Even 172.502(a)(1) (placarding general requirements) records 1,820 citations with an 18.5% OOS rate.
By contrast, 172.331-HMM's 5 all-time citations and 0.0% OOS rate place it at the low end of enforcement severity. It's a technical compliance issue rather than an immediate safety shutdown.
How to avoid it
The co-occurring violations in recent inspections give clear guidance on what inspectors are checking when they find a missing ID number on bulk packages:
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Check hazmat labeling before departure. Our data shows 172.400A2-HML (hazmat labeling on packages) and 172.406C-HML (multiple labels required) appear alongside 172.331-HMM citations. Verify that every bulk package has both the correct label and the required ID number affixed in a visible, legible location. Don't rely on one without the other.
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Inspect the physical condition of markings during pre-trip. Affixed ID numbers must remain readable and secure. Weather, handling, or vibration can degrade or dislodge them. Walk around your load and confirm every bulk package's ID number is intact and visible—don't assume it stayed in place from shipper to your truck.
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Coordinate with shippers on marking responsibility. Many shippers apply the ID number before handing off the load. Verify at pickup that the marking is present and correct. If you're responsible for affixing the ID number, do it before you leave the facility and photograph the result as a record.
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Train on which bulk packages require ID numbers. Not all hazmat requires an ID number in the same format. Know the specific requirements for the commodity you're hauling so you can spot a missing number immediately, rather than waiting for an inspector to find it.
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Perform a final marking check at weigh stations or before inspection. A few seconds scanning each bulk package for a visible, legible ID number can prevent this citation. Make it part of your pre-inspection routine whenever you're being checked for hazmat compliance.