What 173.33(a) means in plain language
Cargo tanks—the specialized containers used to haul liquids, gases, and other hazardous materials—must meet a baseline set of structural and operational standards. FMCSR 173.33(a) covers the general requirements that apply to all cargo tanks before they're loaded and put on the road.
These requirements touch on things like tank construction, fittings, closures, and overall integrity. The regulation doesn't allow shortcuts: if your cargo tank doesn't meet the basic standards, it's not safe to transport hazmat, period. That's why inspectors focus on these fundamentals—a failure here isn't a paperwork issue; it's a safety defect that can lead to spills, leaks, or worse.
If you haul hazmat in a cargo tank, you need to know what condition your tank is in before every trip. This isn't just about passing inspection; it's about keeping yourself and the public safe.
What our enforcement data actually shows
Across our 13 million+ roadside inspection records, we've logged 43 all-time citations for 173.33(a). In the last 12 months, the citation count dropped to 0, and we saw 0 citations in the last 90 days. This code ranks #1675 out of 3,036 FMCSR codes by citation volume—it's not the most frequently cited violation, but when it does get flagged, it's serious.
Here's the critical number: 83.7% of all 173.33(a) citations resulted in an out-of-service order. That means 36 vehicles out of 43 were pulled from service. For context, the all-FMCSR average out-of-service rate is 31.4%. A cargo tank general requirements violation is 2.7 times more likely to land you out of service than the typical FMCSR citation. When an inspector catches a problem with your cargo tank's basic compliance, there's almost no gray area—the tank either passes or it doesn't.
Who gets cited most
Our inspection records show the enforcement activity concentrated among smaller independent operators and regional carriers. The carrier with the highest citation count in our database is Lucio Valenzuela Zamora (USDOT 3862346) with 4 citations. Transportes Y Maquinaria Moro SA de CV, Anselmo Alejandro Perez Ruvalcaba, Enrique Galindo Hernandez, and Rodolfo Arturo Garza Garza each appear with 2 citations in our records.
Because citation volume for this code is low overall, state-level breakdowns are difficult to interpret reliably. What matters is that hazmat cargo tank transport is a specialized operation, and whoever operates in this space needs to treat tank inspection and maintenance as non-negotiable.
Vehicle makes cited include a range of equipment: Kenworth (KW) appears in 7 citations, Freightliner (FRHT) in 6, and various others. The "Other" category accounts for 12 citations, reflecting the diversity of cargo tank configurations on the road.
How severe is this compared to similar codes
Within the Hazardous Materials category, cargo tank violations sit in a different tier than some peer codes:
Placarding and loading violations are much more common. Our data shows 177.834(a)—General loading/unloading hazmat—has 3,839 citations with a 97.9% OOS rate. That code is cited roughly 89 times more often than 173.33(a). Even 177.817(a)—Placarding violation—logs 2,274 citations. These codes reflect the sheer volume of hazmat movements across the country.
But cargo tank structural issues are rarer and equally serious. When an inspector documents a problem with your tank itself under 173.33(a), the consequence is stark: an 83.7% OOS rate. Compare that to 172.502(a)(1)—Placarding general requirements—which has an 18.5% OOS rate. A cargo tank defect is treated as a showstopper; a placard defect is often correctable on the spot.
This reinforces a simple reality: inspectors assume cargo tank violations signal a genuine safety hazard. There's no "fix it later" option.
How to avoid it
If you operate a cargo tank, your best defense is a rigorous pre-trip inspection routine:
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Walk the tank before every load. Check for visible dents, cracks, corrosion, or damage to the shell and fittings. Look at seams, bottom corners, and any weld areas. A dent might be cosmetic; a structural defect is not. If you're unsure, treat it as a reason to have the tank serviced before you move it.
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Test all closures, caps, and fittings. Make sure dome covers and access plates seat properly. Loose or damaged closures can allow cargo to spill and will trigger an inspection failure immediately.
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Verify that all safety devices function. Pressure-relief valves, emergency shutoff devices, and venting systems must be intact and operable. If a seal is cracked or a valve won't move freely, the tank fails basic safety requirements.
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Know your tank's service history. If your cargo tank has been repaired, re-lined, or had fittings replaced, keep that documentation. Inspectors will want to see evidence that repairs meet regulatory standards.
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Don't skip maintenance windows. Cargo tanks are certified equipment. If maintenance is due—whether it's internal cleaning, gasket replacement, or a full inspection cycle—get it done before the tank goes back in service. Once an inspector cites you for a structural defect, you're out of service until it's fixed, and that costs you money and time.
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Partner with a reputable tank service facility. If you own the tank or are responsible for its condition, establish a relationship with a shop that understands FMCSR 173.33(a) requirements. A pre-season or quarterly checkup can catch problems before they become violations.
The bottom line: cargo tank citations are rare, but they're almost always serious. When one lands on you, it's because the tank failed a fundamental safety standard. Your job is to make sure that never happens by treating tank condition as part of your non-negotiable pre-trip ritual.