Periodic inspection and testing is necessary because all electrical installations deteriorate due to a number of factors, i.e. damage, wear, tear, corrosion, excessive electrical loading, ageing and environmental influences. Consequently:

1. legislation requires that electrical installations are maintained in a safe condition and therefore must be periodically inspected and tested
2. licensing authorities, public bodies, insurance companies, mortgage lenders and others may require periodic inspection and testing of electrical installations
3. additionally, periodic inspection and testing should be considered to assess compliance with BS 7671