What 173.33A means in plain language
FMCSR 173.33A covers the basic structural and operational requirements for any cargo tank used to transport hazardous materials. This includes the tank itself, its fittings, valves, vents, and safety devices. Inspectors are looking at whether your cargo tank meets minimum federal standards for safe hazmat transport — things like proper construction, adequate spacing between compartments, working pressure relief systems, and correct installation of required equipment.
When an inspector cites you for 173.33A, they've identified a deficiency in the cargo tank's general condition or configuration that violates federal standards. This could range from structural damage, missing or non-functional safety equipment, to improper tank assembly or maintenance. Because hazardous materials can cause serious harm if released, the standards for cargo tanks are strict and enforcement is serious.
What our enforcement data actually shows
Across our 13 million+ inspection records, 173.33A is cited relatively infrequently — only 35 times all-time, ranking #1735 of 3,036 FMCSR codes by citation volume. In the last 12 months, we've recorded 11 citations, with just 2 in the last 90 days. However, when this code is cited, the consequences are severe: our data shows a 97.1% out-of-service rate, meaning 34 out of 35 citations resulted in the vehicle being placed out of service immediately.
This OOS rate is nearly three times higher than the all-FMCSR average of 31.4%. The gap reflects the hazmat regulatory framework: cargo tank defects are rarely considered minor or deferrable. If your tank doesn't meet federal standards, regulators will not let you continue operating until it's fixed.
Who gets cited most
Our inspection records show that over the last 180 days, Texas accounts for the enforcement activity we track for this code, with 4 citations and a 100.0% out-of-service rate. While the sample size is small, the pattern is consistent with national hazmat enforcement: inspectors remove non-compliant cargo tanks from service without exception.
Looking at carriers all-time, our data shows fleets such as Transfaza SA de CV with 8 citations and Transportes Arlequin SA de CV with 3 citations. This does not imply negligence; small sample sizes in rare-violation categories can reflect routing, volume, or inspection density rather than safety culture. Notably, many carriers in our database have zero citations for this code.
How severe is this compared to similar codes
Within the hazmat category, 173.33A sits in a different enforcement tier than more common violations. For comparison, general loading and unloading hazmat violations (177.834A-HMC) trigger 3,954 citations with a 99.2% OOS rate, and placarding violations (177.817(a)) generate 2,274 citations at 75.1% OOS. The reason 173.33A is cited less often but with near-certain out-of-service action is that cargo tank defects are typically discovered during vehicle inspections and represent irreparable safety gaps that must be corrected before transport resumes.
In contrast, some peer codes like placard deterioration (177.817(e)) have much lower OOS rates (5.2%) because placards can be quickly repaired or replaced at a facility. Cargo tank structural or equipment issues usually require shop-level repair.
How to avoid it
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Perform a detailed pre-trip inspection of your cargo tank. Before every load, physically walk around and under the tank. Check for dents, cracks, corrosion, loose bolts, or leaking seals. Look at all access covers, manway covers, and closures — they must be secure and undamaged. Don't just walk by; open inspection points if accessible and verify they close properly.
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Test all safety devices before departure. Pressure relief valves, emergency shutoff devices, and vent systems must operate smoothly. If a valve sticks, leaks, or doesn't reset, report it to maintenance immediately. Do not leave the yard with a known defect.
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Verify proper tank baffling and compartment isolation. If your cargo tank has multiple compartments, confirm that bulkheads and baffles are in place and secure. Shifting hazmat between compartments during braking or cornering is both a safety and a compliance risk.
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Check all placarding and marking hardware. Placard holders, mounting brackets, and reflectors must be firmly attached and present on all four sides. Our inspection data shows that hazmat violations often cluster — missing or damaged placarding frequently appears alongside cargo tank equipment issues, so don't skip this step.
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Know your tank's DOT/ASME certification status. Verify that your cargo tank has valid inspection stickers and certification marks. If the tank has reached its re-certification interval, get it inspected and certified before it goes back into service. Expired certification is a common trigger for out-of-service orders.
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Report maintenance issues to your carrier immediately. If you notice any crack, weld issue, loose fitting, or non-functional safety device during your trip, stop at a safe location and notify dispatch. Do not attempt to limp a defective cargo tank to the next stop — 97.1% of citations result in immediate out-of-service placement, meaning your load will not move until repair is complete.
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Request scheduled maintenance for your assigned tank. If you regularly drive the same cargo tank, work with your safety manager to ensure routine maintenance is performed at intervals that catch wear before it becomes a violation. Vehicle makes like Kenworth (KW) and other common tank carriers are present in our citation data, indicating no particular brand is exempt — all require consistent upkeep.