Portable Appliance Testing (PAT testing) is the process of checking electrical appliances to establish whether they are safe to use. The term covers a combination of visual inspection and electrical tests carried out on individual pieces of equipment — anything that is plugged into a socket and can be moved.
PAT testing is widely used in workplaces, commercial premises, rented properties, and organisations that own or manage electrical equipment. Employers have a duty under health and safety legislation to ensure that electrical equipment used at work is maintained in a safe condition, and PAT testing is one of the practical methods used to demonstrate this.
Landlords may also arrange PAT testing on appliances provided as part of a furnished tenancy. The tests typically include a visual check of the appliance, its cable, and its plug; an earth continuity test for Class I appliances (those with an earth connection); and an insulation resistance check.
The results indicate whether the appliance is safe to continue using, requires repair, or should be taken out of service. Appliances are usually labelled after testing to show the date of the check and the outcome, and a written record is maintained for each item.
This record provides evidence that equipment has been assessed and helps identify items that are due for re-checking. Not all appliances are tested in the same way.
Class I appliances — those with an earth, such as desktop computers and larger kitchen appliances — require both earth continuity and insulation tests. Class II appliances — those with double insulation, such as many power tools and desk fans — require insulation testing but not earth continuity.
The approach is adapted to the construction of each appliance.