What is PAT testing?

Portable appliance testing (PAT), formally referred to in standards as in-service inspection and testing of electrical equipment, is a process used to verify that electrical equipment remains safe to use throughout its working life.

The process typically involves a combination of visual inspection and, where appropriate, electrical testing, with the scope and frequency determined by the type of equipment, how it is used, and the environment in which it operates. PAT testing is widely used in the United Kingdom and Ireland, and similar practices exist internationally under different names and regulatory frameworks.

Purpose

The purpose of PAT testing is to help reduce the risk of electric shock, burns, and fire arising from the use of electrical equipment. Over time, normal use, handling, and environmental factors can cause deterioration of cables, plugs, insulation, and protective earthing.

Health and safety legislation in many countries does not mandate a specific testing regime, but instead requires that electrical equipment is maintained in a safe condition. PAT testing is one method by which organisations demonstrate that electrical equipment is being routinely checked and maintained as part of an overall electrical safety management system.

Scope of equipment

PAT testing (in-service inspection and testing of electrical equipment) applies to electrical equipment in service, including portable, movable, and fixed or stationary appliances. Inclusion is determined by how equipment is supplied, used, and maintained, rather than solely by whether it is fitted with a plug.

In practice, this commonly includes:

• office equipment such as computers, monitors, and printers

• kitchen and catering appliances, including kettles, microwaves, dishwashers, and refrigerators

• hand-held and portable tools

• extension leads, plug-in power supplies, and portable RCDs

• fixed or stationary appliances connected via a plug, fused connection unit (FCU), switch, or local isolator, where inspection and testing forms part of an in-service maintenance regime

This is distinct from inspection and testing of a building’s fixed electrical installation, such as distribution boards, final circuits, and protective devices, which is typically addressed under separate inspection and testing regimes. In-service inspection and testing may interface with installation testing where defects suggest an upstream issue, but the two activities are not the same.

Inspection and testing process

PAT testing is not a single test, but a process that may include several stages depending on the equipment and the outcome of a risk assessment.

Visual inspection

A visual inspection is carried out to identify obvious signs of damage or deterioration, such as:

• damaged plugs or cable sheathing

• exposed conductors

• cracked or broken casings

• signs of overheating, contamination, or misuse

Visual inspection is considered one of the most effective means of identifying dangerous defects and may, in some cases, be sufficient on its own for maintaining electrical safety.

Electrical testing

Where required, electrical tests may be carried out using suitable test instruments. Depending on the equipment and its construction, this may include:

• verification of protective earthing continuity

• checks on the integrity of insulation

• measurement of leakage or touch current

The specific tests performed, and the acceptable limits applied, vary according to the class of equipment, applicable standards, and the presence of electronic components that may influence test results.

Functional checks

In some cases, a basic functional check is carried out to confirm that the equipment operates as intended and does not exhibit abnormal behaviour during use.

Frequency of testing

There is no universal testing interval that applies to all electrical equipment. Decisions about inspection and testing frequency are typically based on factors such as:

• the type of equipment

• the environment in which it is used

• how often it is handled or subjected to mechanical stress

• the potential consequences of failure

In low-risk environments, routine user checks and periodic visual inspections may be sufficient, whereas higher-risk environments may require more frequent formal inspection and testing.

Competence

PAT testing should be carried out by a competent person – someone with sufficient knowledge and experience to identify hazards, carry out inspections and tests correctly, and interpret the results.

In many jurisdictions, competence does not require an electrician’s qualification. It may instead be achieved through a combination of training, instruction, and practical experience appropriate to the equipment being inspected and the environment in which it is used.

International use and terminology

While “portable appliance testing” is a commonly used term in the United Kingdom and Ireland, similar practices exist internationally:

• In Australia and New Zealand, the process is commonly referred to as “test and tag” and is governed by AS/NZS standards.

• In Germany, in-service testing of electrical equipment is carried out under occupational safety regulations such as DGUV Vorschrift 3.

• In other countries, inspection and testing may form part of broader electrical safety or workplace safety programmes.

Despite differences in terminology and regulation, the underlying objective is consistent: ensuring that electrical equipment remains safe during use.

Summary

PAT testing is a practical method for managing the electrical safety of equipment in service. By combining visual inspection with appropriate electrical testing and risk-based decision-making, organisations can reduce the likelihood of electrical accidents and demonstrate effective maintenance of electrical equipment.