Check that the outer cover of the equipment is not damaged

Check that the outer cover of the equipment is not damaged in a way that will give rise to electrical or mechanical hazards. Experiments carried out on students (with medical staff standing by just in case) have shown that a current of 50mA to 500 mA flowing through the heart is enough to stop your heart. The exact current depends on the individual and the on the frequency of the electrical supply 55Hz supplies can kill you at slightly lower currents than DC supplies or high frequency supplies.