What 172.328E means in plain language
Liquefied petroleum gas (LPG) exists in two forms: odorized and non-odorized. When LPG is not odorized—meaning it lacks the distinctive rotten-egg smell that makes gas leaks obvious to people nearby—the cargo tank carrying it must be clearly marked to indicate this fact. This marking serves a critical safety function: first responders, maintenance personnel, and emergency crews need to know instantly whether they're dealing with odorized or non-odorized LPG, because the absence of an odor warning changes how they assess and respond to a potential leak or accident.
The regulation requires that your cargo tank display the proper marking or label identifying the product as non-odorized LPG. If you're hauling non-odorized LPG and your tank doesn't have this marking, you're in violation. This is a paperwork and labeling violation—not a mechanical defect or operational safety issue—but it's still serious because it defeats the whole purpose of hazmat communication.
What our enforcement data actually shows
Across our database of 13 million roadside inspections, 172.328E has been cited 4 times all-time, with 3 citations in the last 12 months and 0 in the last 90 days. The out-of-service rate for this code is 0.0%: none of the 4 citations resulted in a vehicle being placed out of service. This contrasts sharply with the all-FMCSR average out-of-service rate of 31.4%, meaning 172.328E violations are rarely severe enough to ground a truck on the spot.
Despite its rarity, 172.328E ranks #2480 out of 3,036 FMCSR codes by citation volume, placing it in the bottom tier of enforcement. The most recent activity shows 1 citation in July 2025 and 2 in December 2025, suggesting sporadic enforcement rather than a sustained compliance crackdown.
Who gets cited most
Our inspection records show Texas as the only state with recorded citations for this code in the last 180 days, accounting for 2 citations, both with a 0.0% out-of-service rate. The small sample size limits geographic analysis, but Texas's presence reflects the state's significant LPG transport and petrochemical industry.
Looking at carriers, our data shows fleets such as California Gas Transport Inc (USDOT 589266) with 2 all-time citations and Ahrens Brothers Transport Inc (USDOT 1849284) and Midstream Transportation Company (USDOT 2497677) each with 1 citation. These numbers reflect the carriers that have encountered enforcement for this specific marking violation, not a pattern of systemic non-compliance.
How severe is this compared to similar codes
Hazardous materials violations span a wide severity spectrum. General loading and unloading hazmat violations—codes 177.834A-HMC and 177.834(a)—dwarf 172.328E in both volume (3,954 and 3,839 citations respectively) and consequence, with out-of-service rates of 99.2% and 97.9%. These are operational violations that expose people to immediate danger.
Placarding violations tell a similar story. Code 177.817(a) (placarding violations) has 2,274 citations with a 75.1% out-of-service rate—far more aggressive enforcement. Even code 172.516(c)(6), which addresses placard damage or obscuration, has 1,796 citations but only a 1.6% out-of-service rate, suggesting inspectors treat physical placard condition as a minor issue compared to missing placards entirely.
172.328E's 0.0% out-of-service rate places it among the lowest-consequence codes in the hazmat category, grouped with administrative or documentation-level violations rather than operational safety failures. This suggests inspectors view the marking requirement as important for communication purposes but not an immediate safety threat warranting vehicle shutdown.
How to avoid it
If you transport non-odorized LPG, use these steps before every trip:
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Walk around your entire cargo tank during pre-trip inspection. Check that any required markings or labels for non-odorized LPG are present, visible, and legible. Don't assume they're there from the last trip—weather, wear, and previous repairs can damage them.
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Know your cargo before you load. Confirm with your dispatcher or the shipper whether the LPG you're picking up is odorized or non-odorized. If it's non-odorized, verify that the tank is properly marked before you accept the load.
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Inspect markings for damage or fading. If a marking is faded, peeling, or partially obscured by dirt or ice, treat it as missing. Clean the tank or request that the carrier replace the marking before you depart.
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Don't rely on paperwork alone. The bill of lading or shipping papers may say "non-odorized," but the tank itself must be marked. Roadside inspectors check the physical tank, not your documents.
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If you spot a missing or damaged marking, report it immediately. Don't drive the load. Contact your company's safety department or dispatcher so the tank can be relabeled at the terminal or shipper before you're cited at an inspection.