Load-holding safety valves from Keith Huber Corporation prevent the rear door on vacuum trucks from slamming without warning from hydraulic pressure loss/failure. All of the company’s vacuum units were redesigned and retrofitted with rear door cylinders that prevent the rear door on a unit from closing if hydraulic pressure is suddenly lost to the door cylinders. Along with properly installing the supplied safety props, this prevents an accident from occurring due to the rear door shutting prematurely. 800/334-8237; www.keithhuber.com.