What 173.33(b) means in plain language
173.33(b) governs how hazardous materials must be loaded into cargo tanks. The regulation sets specific requirements for the process of placing cargo into these specialized containers—everything from how the material enters the tank, what precautions must be taken during loading, to how the tank must be positioned and secured during the process.
This isn't about what you carry or where you deliver it. It's specifically about the mechanical and procedural steps involved in getting hazmat into a cargo tank safely. Loading a cargo tank improperly can create spills, overfill conditions, pressure imbalances, or contamination—all of which pose significant safety and environmental risks.
If you were cited for this violation, an inspector observed that your loading procedure, your vehicle setup, or your handling of the transfer process didn't meet federal hazmat standards.
What our enforcement data actually shows
Across our 13 million+ inspection records, 173.33(b) has generated only 4 all-time citations, with 0 citations in the last 12 months and 0 in the last 90 days. This makes it one of the least-cited hazmat regulations in the database, ranking #2480 of 3,036 FMCSR codes by citation volume.
When this violation is cited, the outcome is mixed. Of the 4 all-time citations on record, 1 resulted in an out-of-service order, giving this code a 25.0% OOS rate. That's notably lower than the all-FMCSR average OOS rate of 31.4%, suggesting that when inspectors do cite 173.33(b), they're somewhat less likely to deem the vehicle immediately unsafe for continued operation compared to violations across the entire federal code.
The rarity of this citation makes it harder to spot patterns, but it also suggests that most carriers and drivers are either complying well with loading procedures or that violations tend to be caught and corrected before a roadside inspection occurs.
Who gets cited most
Our records show that KUHNLE BROTHERS INC (USDOT 120682) has received 2 citations for 173.33(b), more than any other carrier in our database. ETCHBERGER TRUCKING INC (USDOT 1499162) and ELITE FUELS TRANSPORTATION INC (USDOT 1890625) each have 1 citation on record. With such a small citation volume overall, no single state or region shows a clear enforcement concentration.
Vehicles cited for this violation were predominantly PTRB-make cargo tanks (3 citations), followed by SAIC units (2 citations). This data reflects the types of equipment most commonly used in hazmat cargo operations, not a quality signal about specific manufacturers.
How severe is this compared to similar codes
173.33(b) sits in the hazardous materials category alongside several other loading and placarding violations, but the enforcement picture is starkly different.
General loading and unloading hazmat violations—codes 177.834A-HMC and 177.834(a)—dwarf 173.33(b) in enforcement volume, with 3,954 and 3,839 citations respectively. Both of those codes carry an OOS rate above 97%, meaning inspectors almost always remove vehicles from service when those violations are found. Placarding violations like 177.817(a) (2,274 citations, 75.1% OOS rate) are also far more common and more likely to result in an immediate out-of-service order.
By contrast, 173.33(b)'s 25.0% OOS rate and minimal citation history suggest it's either a lower-priority enforcement area or one where compliance is already strong. When similar hazmat violations are found, they're treated much more severely.
How to avoid it
Because 173.33(b) is so rarely cited, the best defense is to ensure your loading operation is compliant with written procedures and vendor guidelines:
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Know your cargo tank's loading specifications. Before arriving at a loading facility, confirm the maximum fill level, loading rate, pressure limits, and any special venting requirements for your specific tank. These vary by tank design, age, and certification.
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Inspect the tank and loading connections before any transfer. Check for damage, corrosion, or loose fittings. Confirm that vents, drains, and gauges are clear and functional. A pre-load visual walk-around takes minutes and prevents most loading errors.
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Verify the loading facility's procedures align with your tank's specs. Don't assume the facility operator knows your equipment. Communicate your tank's limits and confirm they match what the facility is about to do.
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Monitor the transfer in real time. Stay near the tank during loading. Watch the pressure gauge or level indicator. Stop the transfer immediately if you see anything abnormal—an unexpected pressure spike, leaking connections, or overflow.
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Never leave a tank unattended during loading or unloading. Your presence and attention are the fastest early warning for spills, overpressure, or incompatible cargo mixing.
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Document your pre-load inspection. Keep notes or photos of tank condition and the facility's loading rate and duration. This record protects you if a problem develops later.