A tank vehicle's valves, manhole covers, and vents are inspection items that the federal knowledge requirement for this endorsement gives no procedure for. What does CDL manual guidance call for?

Explanation

Guidance is to verify every valve position before the vehicle is loaded, emptied, or moved, to confirm the manhole covers carry gaskets and seat properly, to leave the vents unobstructed so they can do their job, and never to drive with an open valve or manhole cover. The reason is that a tank only holds its load while its closures are shut, and a vent that cannot breathe lets pressure build or a vacuum form as the contents move and change temperature. This is manual practice rather than a codified procedure: 49 CFR 383.119(i) makes operating practices and procedures not otherwise specified a required knowledge area for the endorsement, naming no device and setting no step. The wrong options each remove the driver's own check, assuming a valve cannot be disturbed between trips, treating a vent as a leak path to be plugged rather than a pressure path to be kept open, or confining the check to hazardous cargo when the endorsement itself is not limited to hazardous cargo.

Source: 49 CFR 383.119(i)