PAT testing, properly called in-service inspection and testing of electrical equipment, is the routine inspection and electrical testing of portable and movable appliances to confirm they are safe to use. There is no UK law that names PAT testing or sets a fixed interval. The legal duty comes from the Electricity at Work Regulations 1989, which require employers to maintain electrical equipment so as to prevent danger; the IET Code of Practice for In-service Inspection and Testing of Electrical Equipment (5th edition, 2020) is the accepted guidance on how to meet it. Frequency is decided by risk assessment, tests differ for Class I and Class II equipment, and every test should be recorded against a uniquely identified appliance.
- No statutory interval: the Electricity at Work Regulations 1989 require equipment to be maintained; the IET Code of Practice (5th ed., 2020) explains how.
- Intervals are risk-based; the Code gives commonly used starting points, from 3 months for construction site tools to 48 months for office IT.
- Class I equipment needs an earth continuity test; Class II does not.
- Records should identify each appliance, the tests, the results, the date and the next due date.
- Anyone competent can test; electricians already hold the knowledge, and City & Guilds 2377 is the common qualification.
What is PAT testing?
PAT stands for portable appliance testing, a term that has stuck even though the IET dropped it from the title of its Code of Practice because the scope covers far more than portable items: hand-held, portable, movable, stationary, fixed and built-in equipment, IT equipment and extension leads. In-service means the periodic checks done during the equipment's working life.
The process has three levels:
- User checks: the user looks for damage before use and reports faults; no record unless a fault is found.
- Formal visual inspection: a competent person examines the appliance, plug and flex for damage, correct fuse, cable grip and overheating, and records the result. The Code notes that most faults are found visually.
- Combined inspection and test: the formal visual inspection plus electrical tests with a PAT instrument, recorded.
Is PAT testing a legal requirement?
Not by name. Three pieces of legislation create the duty:
- Health and Safety at Work etc. Act 1974: general duty on employers to ensure the health and safety of employees and others.
- Electricity at Work Regulations 1989: Regulation 4(2) requires all systems to be maintained so far as reasonably practicable to prevent danger. "System" includes the equipment plugged into it.
- Provision and Use of Work Equipment Regulations 1998: work equipment must be maintained in an efficient state and good repair.
None of these specify a method or interval. The Health and Safety Executive's guidance, Maintaining portable electric equipment in low-risk environments (INDG236), states explicitly that the law does not require every item to be tested annually and that frequency should be proportionate to risk. The IET Code of Practice provides the detail, and following it is the standard way for a duty holder to show that equipment is being maintained.
The duty holder is the person with control over the equipment: the employer, the landlord of a furnished let, the facilities manager, or a self-employed person for their own tools. PAT testing covers what is plugged in; the fixed wiring is covered by an EICR under Chapter 65 of BS 7671 (see how often an EICR is required), and a duty holder needs both.
How often should PAT testing be done?
The 5th edition of the Code of Practice moved firmly to a risk-based approach: the duty holder sets intervals from the equipment type, its class, the environment, how and by whom it is used, and the history of previous results. The 5th edition dropped the earlier edition's table of suggested initial frequencies; the values below are the intervals many duty holders still use as a starting point. They are not statutory and should be adjusted once you have results to look at.
| Environment | Equipment type | Formal visual inspection | Combined inspection and test |
|---|---|---|---|
| Construction site (110 V) | Hand-held tools, portable equipment, extension leads | Monthly | Every 3 months |
| Industrial, including commercial kitchens | Hand-held and portable, Class I | Monthly | Every 6 to 12 months |
| Industrial | Movable, stationary, IT | Monthly | Every 12 months |
| Equipment used by the public (e.g. launderettes, hire) | Hand-held and portable, Class I | Weekly to monthly | Every 6 months |
| Schools | Hand-held Class I | Every 4 months | Every 12 months |
| Schools | IT and stationary equipment | Every 12 months | Up to 48 months |
| Hotels and residential care | Hand-held and portable, Class I | Every 6 to 12 months | Every 12 to 24 months |
| Offices and shops | Hand-held and portable, Class I | Every 12 months | Every 24 months |
| Offices and shops | IT equipment, Class II, stationary | Every 24 months | Every 24 to 48 months, or none if visual results are consistently good |
The harsher the environment and the more the item is handled, the shorter the interval. The Code allows intervals to be lengthened where a run of results shows no faults, expects them to be shortened where damage is found, and makes clear that some low-risk Class II equipment may only ever need visual inspection.
What tests are carried out on Class I and Class II equipment?
Equipment class determines which tests apply. Class I equipment depends on its earth connection for shock protection: exposed metalwork is connected to the protective conductor so a fault is cleared by the fuse. Class II equipment has double or reinforced insulation, no earth connection, and the double-square symbol. Class III runs on separated extra-low voltage and generally needs only a visual inspection.
| Test | Class I | Class II | What it checks | Typical pass criterion |
|---|---|---|---|---|
| Formal visual inspection | Yes | Yes | Damage to case, flex, plug; correct fuse; cable grip; signs of overheating | No damage; fuse appropriate to the appliance |
| Earth continuity | Yes | No | Low-resistance path from plug earth pin to exposed metalwork | Commonly 0.1 Ω plus the resistance of the flex, measured with a low or high test current |
| Insulation resistance | Yes | Yes | Insulation between live conductors and earth or the case | At 500 V d.c., commonly 1 MΩ minimum for Class I and 2 MΩ for Class II |
| Protective conductor current or touch current | Alternative | Alternative | Leakage under normal operation, used where an insulation test could damage electronics | Per the Code's limits for the equipment type |
| Polarity (leads and extension leads) | Yes | Yes | Correct wiring of the lead | Correct |
| Functional check | Yes | Yes | The appliance works and switches correctly | Operates normally |
Insulation resistance can be measured at 250 V d.c. for equipment with surge protection or sensitive electronics, and the protective conductor current or touch current test is used where the 500 V test would be inappropriate. Extension leads are tested as Class I items in their own right. The instrument should be calibrated, and the tester should read trends: an earth continuity result that has risen year on year on the same drill suggests a flex on its way out, even if it is still within the limit.
What should be recorded?
The Code recommends an asset register plus a test record for each item, containing:
- A unique appliance identifier (usually printed on the label).
- Description, make and model, and location or department.
- Equipment class.
- The inspection and tests carried out, with measured values, not just pass or fail.
- Result: pass or fail, and any remedial action such as a replaced plug or fuse.
- Name of the person carrying out the test, the instrument used and its calibration status.
- Date of test and next due date, based on the risk assessment.
Keep the records for the life of the equipment. A record of failed items and what happened to them is as important as the passes; an auditor wants to see that a failed kettle was withdrawn.
What about labels?
Labels are not a legal requirement, but the Code of Practice recommends them. A pass label typically shows the appliance identifier, the date tested, the next due date and the tester's initials or company, and links the item to the record. Failed items should receive a distinct failed label and be removed from use immediately. A label is a pointer; the register with the measured values is the evidence.
Who can carry out PAT testing?
There is no mandatory qualification for PAT testing; the Electricity at Work Regulations 1989 require a person with the knowledge and experience to avoid danger. A competent person needs to be able to:
- Recognise equipment classes and decide which tests apply.
- Use the PAT instrument correctly and understand its limitations.
- Interpret measured values and marginal readings.
- Recognise damage and unsafe equipment on visual inspection.
- Decide on and justify test intervals.
Electricians already have the underlying knowledge and often add PAT testing to EICR work for commercial clients. Non-electricians such as caretakers and IT staff can be competent for lower-risk environments with training; the City & Guilds 2377 award is the common benchmark. Whoever does it, the duty holder remains responsible; hiring a tester does not transfer the duty.
How Certio helps
Certio produces the EICR, EIC, Minor Works certificate and PAT records on the BS 7671 model forms and turns them into branded PDFs. Photograph the consumer unit and the circuit schedule drafts itself; point the phone camera at a Megger MFT-X1 and the reading goes straight into the schedule of test results, or dictate it while your hands stay on the probes. Suggested observation wording with the regulation reference is there for you to check and confirm. The judgement stays yours; the typing goes. Starter is free for 7 days, then £5 a month.