FMCSR 172.505(b) — Not Placarded for Subsidiary Corrosive

Yes. Across our 13 million inspection records, every instance of 172.505(b) cited resulted in an out-of-service placement—a 100.0% OOS rate. This is significantly more severe than the 31.4% national average OOS rate across all FMCSR codes. When inspectors cite this violation, they immediately remove the vehicle from operation until the hazmat placarding deficiency is corrected.

This is among the most serious placarding violations. Our data shows 172.505(b) carries a 100.0% out-of-service rate, far exceeding related placarding violations: 172.516(c)(6) (damaged placard) sits at 1.6% OOS, and 172.502(a)(1) (general placarding) is 18.5%. The only peer codes more severe are general hazmat loading violations (177.834A-HMC at 99.2% and 177.834(a) at 97.9%). This reflects the regulatory weight placed on subsidiary corrosive placarding—it directly impacts emergency responder safety.

Our inspection database shows zero citations for 172.505(b) in the last 12 months and zero in the last 90 days. All-time, only 2 citations appear in our 13 million+ record set. This rarity does not indicate leniency—it likely reflects industry compliance with this hazmat placarding requirement. However, when it is cited, enforcement is absolute: both historical cases resulted in immediate out-of-service orders.

1. Stop operation immediately. The vehicle is out of service until corrected.
2. Verify the hazmat commodity. Confirm whether your load requires subsidiary corrosive placarding under DOT hazmat rules.
3. Obtain and apply the correct placard(s). Subsidiary corrosives require specific marking distinct from primary hazard placards.
4. Document the fix. Take photos of the corrected placarding before requesting reinspection.
5. Request a reinspection through your state DOT or the inspecting agency to clear the out-of-service status.
6. Notify your carrier/dispatcher. This affects both driver and carrier safety records.

This violation is extremely rare in our dataset. All-time, we've recorded only 2 citations for 172.505(b) across 13 million inspections. Ranked #2651 out of 3,036 FMCSR codes by citation volume, it represents less than 0.1% of hazmat placarding enforcement. The two carriers cited were FAROOQ TRUCKING INC and TEN M OIL FIELD SERVICES LLC, each with one citation. Rarity suggests most carriers comply, but the 100% OOS rate means enforcement, when it occurs, is uncompromising.

You can challenge a citation through the DataQs (FMCSA's Record Dispute Resolution) system if you believe the inspector's finding is factually incorrect. Placarding violations are equipment/documentation findings, not driver behavior infractions. Your dispute should focus on whether the load actually required subsidiary corrosive placarding under the specific commodity being transported. Document the hazmat shipping papers, commodity classification, and placarding requirements at the time of inspection. DataQs review is administrative; you'll need clear evidence to overturn an out-of-service determination.

Subsidiary corrosive placarding alerts emergency responders to secondary hazards when a primary hazard takes precedence. A load might be labeled as "Flammable Liquid" but also contain corrosive properties—that subsidiary marking is critical for first responders deciding how to handle a spill or fire. The 100.0% out-of-service enforcement rate we see reflects DOT's position: missing subsidiary corrosive placards are not minor paperwork issues, they're safety gaps that directly compromise emergency response. This is why every case in our records resulted in immediate vehicle removal.

Both. FMCSA assigns hazmat violations to both the driver and the carrier in CSA safety records. A 172.505(b) citation affects the driver's profile (linked to the safety BASIC categories for hazmat) and the carrier's profile simultaneously. Your safety record and the company's record both reflect the violation. This is why carriers often conduct hazmat refresher training company-wide after a single citation—the enforcement impact extends to the entire operation and can affect the carrier's ratings, audits, and insurance costs.