Nothing like a “thermal event” in one of my test labs at work to spice up the day. A shorted motor in a test fixture induced a failure in the circuit board that was controlling it producing enough heat to melt everything in the vicinity resulting in a plume of acrid smoke. Before releasing a product we conduct a battery of stress tests to ensure the quality of our designs. These tests run 24/7 in unoccupied labs. In this case we were testing a wheel assembly and after 2000 hours of operation the brushes in the motor wore out and the springs which support them shorted together. Far better that we discover this failure mode in our labs rather than in a customer’s home and the incident will result in design improvements and a new smoke detection/power interruption system for all our test labs.