Portable appliance testing generally refers to any electrical item moveable handheld or fixed which is normally connected to a mains supply via a removable plug (mains plug).  During use, these items can deteriorate, mains leads, plugs, cord grips, cabinets and casings etc can become damaged during use increasing the risk of severe or fatal shock to the user.

Mains plug fuses are used to protect the supply cord of the appliance, incorrect fuse types could result in overheating or deterioration of the lead, thus increasing the risk of shock or fire.  Many modern appliances use double insulation, i.e. only two cores are used live and neutral, as no Earth is used.  The insulation of these items is relied upon so as to safeguard the shock risk; regular Pat Tests ensures that this insulation has not deteriorated.  Items such as fridges, microwaves, washing machines or other items with metal cabinets employ three cores; Live, Neutral and Earth.

To eliminate the possibility of the metal becoming live, it is imperative that the Earth bond is maintained; again the Pat Tester and his equipment check that a good Earth Bond is present.