The training requirement
Under 49 CFR 172.704, every hazmat employee must be trained and tested in general awareness, function-specific duties, safety, and security awareness, plus in-depth security training where a security plan is required and driver training for anyone operating a hazmat vehicle. New employees or employees changing functions have 90 days to complete the training, and they may work only under direct supervision until it is done. Recurrent training is required at least once every three years, and the employer must keep training records covering the current cycle and the preceding three years, for 90 days past employment.
The tank certificate
The truck is only half the compliance picture. Cargo tanks hauling hazardous materials must pass the inspection and testing regime in 49 CFR Part 180, including the periodic internal and external inspections and pressure tests on the required cycle, and the tank must carry a current certificate of inspection. A tank that has been patched, welded, or modified outside the certificate is a tank that will stop the truck at the scale or worse, on the road.
Cleaning is a confined space job
Tank cleaning is where the hazmat operation meets the confined space rules. OSHA treats tank interiors as permit-required confined spaces under 29 CFR 1910.146: the atmosphere inside a tanker that carried acid or produced water can be hazardous, and the residues can include vapors, sludge, and in sour service, pyrophoric iron sulfide. Cleaning requires atmospheric testing, ventilation, an attendant, and a permit before entry. The crew that cleans the tanker is doing one of the most hazardous jobs in the oilfield, and the paperwork has to prove the hazard was controlled.
Hazmat compliance is a paperwork operation wrapped around a physical one: training records, tank certificates, bills of lading, and cleaning permits. The same record discipline that keeps custody transfer honest and the ELD log accurate applies here, with higher stakes. If the hazmat file is a binder nobody audits, an operations audit will find the gap between the certificate and the truck.